"gc current grant busy" waits
We've recently upgraded our primary production database from 8i to a 10g RAC cluster on new hardware. This was accomplished by an 8i export and 10g import.
Besides the usual small hiccups, we've got pretty heavily used SQL that is performing very poorly, judging by the statistics. In particular, we're seeing some relaticely simple inserts have over 50% of the time spent in "gc current grant busy".
The SQL is:
INSERT INTO DAILY_USE_STATISTICS
(DAILY_USE_STATISTICS_ID,DAY,MONITORED_ITEM_OWNER_ID,ROLLED_UP)
VALUES (:1,:2,:3,:4)
There is a primary key constraint on DAILY_USE_STATISTICS_ID.
There are foreign key constraints on DAILY_USE_STATISTICS_ID and MONITORED_ITEM_OWNER_ID.
And there is a uniqueness constraint on (DAY, MONITORED_ITEM_OWNER_ID).
Frankly, I don't understand what this wait event is telling me and haven't yet found a description of it in the 10g documentation.
My first suspicion was a problem with freelists, but it was my understanding that ASSM took care of that. Is there an issue with imported data that prevents ASSM from managing freelists for the cluster? Do I have to fix my freelists on these table somehow?
Another theory floating in the office is that we need to increase INI_TRANS, which is currently 1, that we're running out ITLs and waiting on some sort of larger lock, but that doesn't make sense to me; that should show up as a dominating wait event.
Anybody have any clues for me...?
Oh, ALL_TABLES tells me:
PCT_FREE = 10
PCT_USED = null
INI_TRANS = 1
MAX_TRANS = 255
FREELISTS = null
FREELIST_GROUPS = null
NUM_ROWS = 978636
NUM_FREELIST_BLOCKS = 0
LAST_ANALYZED = (today)
Thank you for your suggest. This is a developmnet DB. I think problem was due to out agent that were be down for 24 hours, when DB came online agent have dumped many data creating all those connections.
But if ASH views need a license, normally what have to be used?
Thanks
Stefano
Similar Messages
-
Hi ,
I have two node Oracle RAC.Version is 11.2.0.2
When i do an online inquire transaction for higher load, I am observing 'gc current block busy' in AWR as one of the top events.GV$SESSION_WAIT
doesnt show anything as below.
Kindly let me know how to tune it.
AWR top events.
DB CPU 32 64.34
log file sync 5,972 9 2 18.36 Commit
gc current block busy 2,448 7 23 13.32 Cluster
gc current block 2-way 4,665 3 1 5.41 Cluster
gc current grant busy 2,446 1 0 2.20 Cluster
SQL> SELECT
INST_ID,
EVENT,
P1 FILE_NUMBER,
P2 BLOCK_NUMBER,
WAIT_TIME
FROM
GV$SESSION_WAIT
WHERE
EVENT IN ('buffer busy global cr', 'global cache busy',
'buffer busy global cache');
2 3 4 5 6 7 8 9 10 11
no rows selectedThanksuser10698496 wrote:
I have two node Oracle RAC.Version is 11.2.0.2
When i do an online inquire transaction for higher lRoad, I am observing 'gc current block busy' in AWR as one of the top events.GV$SESSION_WAIT
doesnt show anything as below.
Kindly let me know how to tune it.(Note: Your query against v$session_Wait doesn't seem to match the events listed in the AWR.)
(Note 2: Your snapshot seems to be for a very short time - which doesn't really give an idea of how serious the problem may be in the bigger picture.)
There are many GC events that you won't see in v$session_wait because the session doesn't know the event consuming the time until after the wait has completed - so when you check v$session_wait you will often see "gc cr request", or "gc current request" (I think I may have the names wrong, but I don't have an instance in front of me right now) - these are known as "placeholders" to Oracle and may change to things like "gc current block 2-way" or "gc current block 3-way".
You've looked at the ADDM (so you're licensed for the diagnostic), and seen the top object. Had you not done so I would have suggested looking at the "Segments by .." sections of the AWR report, checking the two sections on CR and CUR traffic; then check the "SQL ordered by ...." sections for the sections on global cache time. If your offenders are insert statements that match primary key indexes then you probably need to stop the instances from inserting into the same index leaf block at the same time.
A key question to ask is whether the primary key is a meaningless value generated by an Oracle sequence; if so have you set the sequence cache size to a large enough value (in the order of thousands or tens of thousands). This is the first step in resolving sequence-based RAC issues. (There are other strategies - but we need more information to determine best action.)
Regards
Jonathan Lewis
P.S. The best place on the Internet for information about details of how RAC works and the interpretation of RAC events is probably Riyaj Shamsudeen's blog at: http://orainternals.wordpress.com/
Edited by: Jonathan Lewis on May 14, 2012 8:24 AM -
How to tune gc cr block 2-way and gc current grant 2-way
Hi,
I'm working on an Oracle Database 11g Release 11.1.0.6.0 - 64bit Production With the Real Application Clusters option, Standard Edition.
During last days I'm suffering performance lack due to 2 main wait event classes:
gc cr block 2-way
gc current grant 2-way
I noticed also this one:
gc buffer busy acquire
Do you have any suggestion on how to check and tune my RAC to reduce those wait events?
Any usefull link?
Thanks in advance,
Samuel
Edited by: Samuel Rabini on Mar 30, 2012 2:39 PMHi;
Please check below which could be helpful for your issue:
RAC Database Running Slow to Hang With High Cluster Wait Due to Small Buffer Cache [ID 1280889.1]
Regard
Helios -
Hi,
Version : Oracle 9i
I am getting buffer busy waits on some tables. Will increase in inittrans & pctfree of those tables reduce buffer busy waits?
Tablespace is having segment space mgmt auto & extent management local.
cursor_sharing is similar.
Users are not experiencing any problem.Is there any problem other than this in statspack report?
STATSPACK report for
DB Name DB Id Instance Inst Num Release Cluster Host
AHD 3712247982 ahd 1 9.2.0.1.0 NO SBGSDPRI
Snap Id Snap Time Sessions Curs/Sess Comment
Begin Snap: 20 13-Feb-07 14:48:35 33 9.9
End Snap: 21 13-Feb-07 15:12:19 34 10.4
Elapsed: 23.73 (mins)
Cache Sizes (end)
~~~~~~~~~~~~~~~~~
Buffer Cache: 656M Std Block Size: 8K
Shared Pool Size: 152M Log Buffer: 768K
Load Profile
~~~~~~~~~~~~ Per Second Per Transaction
Redo size: 5,960.83 2,761.29
Logical reads: 2,376.85 1,101.05
Block changes: 35.48 16.44
Physical reads: 97.56 45.20
Physical writes: 1.15 0.53
User calls: 92.63 42.91
Parses: 20.00 9.27
Hard parses: 0.29 0.13
Sorts: 4.80 2.22
Logons: 0.01 0.00
Executes: 23.14 10.72
Transactions: 2.16
% Blocks changed per Read: 1.49 Recursive Call %: 14.69
Rollback per transaction %: 0.00 Rows per Sort: 472.64
Instance Efficiency Percentages (Target 100%)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Buffer Nowait %: 99.65 Redo NoWait %: 100.00
Buffer Hit %: 95.90 In-memory Sort %: 100.00
Library Hit %: 99.15 Soft Parse %: 98.55
Execute to Parse %: 13.57 Latch Hit %: 99.70
Parse CPU to Parse Elapsd %: 90.83 % Non-Parse CPU: 96.58
Shared Pool Statistics Begin End
Memory Usage %: 84.68 84.76
% SQL with executions>1: 77.32 79.22
% Memory for SQL w/exec>1: 90.74 92.81
Top 5 Timed Events
~~~~~~~~~~~~~~~~~~ % Total
Event Waits Time (s) Ela Time
CPU time 125 54.23
db file sequential read 83,110 69 30.14
db file scattered read 23,196 27 11.75
buffer busy waits 11,760 6 2.42
log file sync 3,078 1 .45
Wait Events for DB: AHD Instance: ahd Snaps: 20 -21
-> s - second
-> cs - centisecond - 100th of a second
-> ms - millisecond - 1000th of a second
-> us - microsecond - 1000000th of a second
-> ordered by wait time desc, waits desc (idle events last)
Avg
Total Wait wait Waits
Event Waits Timeouts Time (s) (ms) /txn
db file sequential read 83,110 0 69 1 27.0
db file scattered read 23,196 0 27 1 7.5
buffer busy waits 11,760 0 6 0 3.8
log file sync 3,078 0 1 0 1.0
log file parallel write 5,216 4,841 1 0 1.7
control file sequential read 1,390 0 1 1 0.5
control file parallel write 462 0 0 1 0.2
db file parallel write 672 336 0 0 0.2
latch free 54 24 0 2 0.0
SQL*Net more data to client 1,026 0 0 0 0.3
LGWR wait for redo copy 12 0 0 0 0.0
SQL*Net message from client 131,863 0 22,857 173 42.9
virtual circuit status 48 48 1,497 31188 0.0
wakeup time manager 45 45 1,446 32123 0.0
SQL*Net message to client 131,864 0 0 0 42.9
SQL*Net more data from clien 27 0 0 0 0.0
Background Wait Events for DB: AHD Instance: ahd Snaps: 20 -21
-> ordered by wait time desc, waits desc (idle events last)
Avg
Total Wait wait Waits
Event Waits Timeouts Time (s) (ms) /txn
log file parallel write 5,216 4,841 1 0 1.7
control file parallel write 462 0 0 1 0.2
control file sequential read 184 0 0 2 0.1
db file parallel write 672 336 0 0 0.2
log file sync 24 0 0 0 0.0
db file sequential read 1 0 0 8 0.0
LGWR wait for redo copy 12 0 0 0 0.0
rdbms ipc message 12,386 7,345 10,752 868 4.0
SQL*Net message from client 384 0 1,498 3901 0.1
smon timer 4 4 1,229 ###### 0.0
SQL*Net message to client 384 0 0 0 0.1
SQL ordered by Gets for DB: AHD Instance: ahd Snaps: 20 -21
-> End Buffer Gets Threshold: 10000
-> Note that resources reported for PL/SQL includes the resources used by
all SQL statements called within the PL/SQL code. As individual SQL
statements are also reported, it is possible and valid for the summed
total % to exceed 100
CPU Elapsd
Buffer Gets Executions Gets per Exec %Total Time (s) Time (s) Hash Value
1,269,773 52 24,418.7 37.5 27.03 76.26 3370382957
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"SYS_B_07" OR id = :"SYS_B_08" OR id = :"SYS_B_09" OR id = :"SYS
117,569 7 16,795.6 3.5 0.52 0.52 1972089848
SELECT call_req.open_date, call_req.id FROM call_req, ctct WHERE
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100,276 4 25,069.0 3.0 2.77 6.95 771782876
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95,832 4 23,958.0 2.8 2.13 3.80 1755292198
SELECT call_req.open_date, call_req.id FROM call_req, ctct, loc,
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86,680 10 8,668.0 2.6 7.69 8.21 3407388950
SQL ordered by Gets for DB: AHD Instance: ahd Snaps: 20 -21
-> End Buffer Gets Threshold: 10000
-> Note that resources reported for PL/SQL includes the resources used by
all SQL statements called within the PL/SQL code. As individual SQL
statements are also reported, it is possible and valid for the summed
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CPU Elapsd
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57,682 191 302.0 1.7 3.48 3.52 484128938
SELECT cnote.posted_date, cnote.text FROM cnote WHERE ( ( cnote.
loc_id = :"SYS_B_0" ) OR cnote.loc_id IS NULL ) AND ( cnote.inte
rnal IS NULL OR cnote.internal != :"SYS_B_1" ) ORDER BY cnote.p
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52,146 3 17,382.0 1.5 1.22 3.60 930247717
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43,534 4 10,883.5 1.3 2.05 2.10 2363733805
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SQL ordered by Reads for DB: AHD Instance: ahd Snaps: 20 -21
-> End Disk Reads Threshold: 1000
CPU Elapsd
Physical Reads Executions Reads per Exec %Total Time (s) Time (s) Hash Value
81,653 52 1,570.3 58.8 27.03 76.26 3370382957
SELECT call_req.open_date, call_req.id FROM call_req, ctct, loc,
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15,402 10 1,540.2 11.1 5.95 17.44 1650906216
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CPU Elapsd
Physical Reads Executions Reads per Exec %Total Time (s) Time (s) Hash Value
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1,540 1 1,540.0 1.1 0.56 1.64 2582352638
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1,106 2 553.0 0.8 1.25 3.01 548248759
SELECT call_req.open_date, call_req.id FROM call_req WHERE ( ( c
all_req.assignee IS NOT NULL OR call_req.group_id IS NOT NULL )
AND ( call_req.type = :"SYS_B_00" OR call_req.type = :"SYS_B_01"
OR call_req.type IS NULL ) AND call_req.active_flag = :"SYS_B_0
2" ) AND ( call_req.group_id IN ( SELECT id FROM ctct WHERE id =
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SELECT call_req.open_date, call_req.id FROM call_req WHERE ( ( c
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473 1 473.0 0.3 1.80 5.57 3376831664
BEGIN statspack.snap; END;
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CPU per Elap per
Executions Rows Processed Rows per Exec Exec (s) Exec (s) Hash Value
7,741 7,738 1.0 0.00 0.00 1060224445
SELECT grpmem.group_id , grpmem.manager_flag , grpmem.member , g
rpmem.notify_flag FROM grpmem WHERE grpmem.id = :"SYS_B_0"
2,459 2,459 1.0 0.00 0.00 3026674282
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ime , att_evt.first_fire_time , att_evt.group_name , att_evt.las
t_mod_dt , att_evt.num_fire , att_evt.obj_id , att_evt.persid ,
att_evt.start_time , att_evt.status_flag , att_evt.user_smag , a
tt_evt.wait_time FROM att_evt WHERE att_evt.id = :"SYS_B_0"
1,336 1,336 1.0 0.00 0.00 3034229510
SELECT cr_prp.description , cr_prp.label , cr_prp.last_mod_by ,
cr_prp.last_mod_dt , cr_prp.owning_cr , cr_prp.persid , cr_prp.r
equired , cr_prp.sample , cr_prp.sequence , cr_prp.value FROM cr
prp WHERE crprp.id = :"SYS_B_0"
968 968 1.0 0.00 0.00 3460529092
select t.name, (select owner_instance from sys.aq$_queue_table_
affinities where table_objno = t.objno) from system.aq$_queue
_tables t where t.name = :1 and t.schema = :2 for update skip lo
cked
808 808 1.0 0.00 0.00 3346182257
SELECT call_req.active_flag , call_req.affected_rc , call_req.as
signee , call_req.call_back_date , call_req.call_back_flag , cal
l_req.category , call_req.change , call_req.charge_back_id , cal
l_req.close_date , call_req.created_via , call_req.customer , ca
ll_req.description , call_req.event_token , call_req.extern_ref
720 720 1.0 0.00 0.00 140137628
Module: Spotlight On Oracle, classic
SELECT DECODE(:b1,'BL','Buffer hash table instance lock','CF','C
ontrol file schema global enqueue lock','CI','Cross-instance fun
ction invocation instance lock','CS','Control file schema global
enqueue lock','CU','Cursor bind lock','DF','Data file instance
lock','DL','Direct loader parallel index create','DM','Mount/sta
718 718 1.0 0.00 0.00 4078915446
SELECT options.app_name, options.sym, options.id FROM options WH
ERE ( options.sym = :"SYS_B_0" ) AND ( options.del = :"SYS_B_1"
) ORDER BY options.app_name
634 634 1.0 0.00 0.00 1199698393
SELECT loc.alias , loc.del , loc.l_addr1 , loc.l_addr2 , loc.l_a
ddr3 , loc.l_addr4 , loc.l_addr5 , loc.l_addr6 , loc.l_details ,
loc.l_name , loc.l_si_id , loc.last_mod , loc.persid , loc.z_cb
SQL ordered by Executions for DB: AHD Instance: ahd Snaps: 20 -21
-> End Executions Threshold: 100
CPU per Elap per
Executions Rows Processed Rows per Exec Exec (s) Exec (s) Hash Value
l1 , loc.zcb_l2 , loc.z_cb_l3 , loc.z_l_code , loc.z_ro_code ,
loc.z_zo_code FROM loc WHERE loc.id = :"SYS_B_0"
531 208 0.4 0.00 0.00 800192270
SELECT lrel.l_persid, lrel.l_attr, lrel.l_sql, lrel.r_persid, lr
el.r_attr, lrel.r_sql, lrel.id FROM lrel WHERE lrel.l_persid = :
"SYS_B_0" and lrel.l_attr = :"SYS_B_1" ORDER BY lrel.l_persid ,
lrel.l_attr , lrel.l_sql
438 438 1.0 0.00 0.00 1317334374
Select PROPERTY_NAME,PROPERTY_VALUE,PROPERTY_TYPE from CI_PROPER
TIES where PROPERTY_NAME=:"SYS_B_0"
429 8,151 19.0 0.00 0.00 1976028604
SELECT cr_stat.sym, cr_stat.code FROM cr_stat WHERE cr_stat.del
= :"SYS_B_0" ORDER BY cr_stat.sym
383 383 1.0 0.00 0.00 2599265718
DELETE FROM anima WHERE id = :"SYS_B_0"
359 359 1.0 0.00 0.00 1719939797
DELETE FROM att_evt WHERE id = :"SYS_B_0"
337 337 1.0 0.00 0.00 3069423312
SELECT anima.a_act , anima.a_delta , anima.a_lock , anima.a_name
, anima.a_org , anima.a_string , anima.a_time , anima.t_method
, anima.t_persid , anima.t_type FROM anima WHERE anima.id = :"SY
S_B_0"
332 331 1.0 0.00 0.00 1549656119
SELECT crsq.id FROM crsq WHERE crsq.code = :"SYS_B_0"
315 315 1.0 0.00 0.00 1734736338
UPDATE cr_prp SET last_mod_by = :"SYS_B_0" , last_mod_dt = :"SYS
_B_1" WHERE id = :"SYS_B_2"
308 1,580 5.1 0.00 0.00 618252548
SELECT cr_prp.sequence, cr_prp.id FROM cr_prp WHERE cr_prp.ownin
g_cr = :"SYS_B_0" ORDER BY cr_prp.sequence
279 1,716 6.2 0.00 0.00 749386807
SELECT call_req.open_date, call_req.id FROM call_req WHERE call_
req.customer = :"SYS_B_0" AND call_req.active_flag = :"SYS_B_1"
ORDER BY call_req.open_date DESC
277 277 1.0 0.00 0.00 321149819
INSERT INTO anima ( a_act, a_delta, a_lock, a_name, a_org, a_str
ing, a_time, t_method, t_persid, t_type, id ) VALUES ( :"SYS_B_
0" , :"SYS_B_1" , :"SYS_B_2" , :"SYS_B_3" , :"SYS_B_4" , nu
ll , :"SYS_B_5" , :"SYS_B_6" , :"SYS_B_7" , :"SYS_B_8" , :"
SQL ordered by Parse Calls for DB: AHD Instance: ahd Snaps: 20 -21
-> End Parse Calls Threshold: 1000
% Total
Parse Calls Executions Parses Hash Value
7,733 7,741 27.15 1060224445
SELECT grpmem.group_id , grpmem.manager_flag , grpmem.member , g
rpmem.notify_flag FROM grpmem WHERE grpmem.id = :"SYS_B_0"
2,459 2,459 8.63 3026674282
SELECT act_log.action_desc , act_log.analyst , act_log.call_req_
id , act_log.description , act_log.internal , act_log.knowledge_
session , act_log.knowledge_tool , act_log.last_mod_dt , act_log
.persid , act_log.system_time , act_log.time_spent , act_log.tim
e_stamp , act_log.type FROM act_log WHERE act_log.id = :"SYS_B_0
1,449 1,449 5.09 3299996875
SELECT att_evt.cancel_time , att_evt.event_tmpl , att_evt.fire_t
ime , att_evt.first_fire_time , att_evt.group_name , att_evt.las
t_mod_dt , att_evt.num_fire , att_evt.obj_id , att_evt.persid ,
att_evt.start_time , att_evt.status_flag , att_evt.user_smag , a
tt_evt.wait_time FROM att_evt WHERE att_evt.id = :"SYS_B_0"
1,336 1,336 4.69 3034229510
SELECT cr_prp.description , cr_prp.label , cr_prp.last_mod_by ,
cr_prp.last_mod_dt , cr_prp.owning_cr , cr_prp.persid , cr_prp.r
equired , cr_prp.sample , cr_prp.sequence , cr_prp.value FROM cr
prp WHERE crprp.id = :"SYS_B_0"
808 808 2.84 3346182257
SELECT call_req.active_flag , call_req.affected_rc , call_req.as
signee , call_req.call_back_date , call_req.call_back_flag , cal
l_req.category , call_req.change , call_req.charge_back_id , cal
l_req.close_date , call_req.created_via , call_req.customer , ca
ll_req.description , call_req.event_token , call_req.extern_ref
718 718 2.52 4078915446
SELECT options.app_name, options.sym, options.id FROM options WH
ERE ( options.sym = :"SYS_B_0" ) AND ( options.del = :"SYS_B_1"
) ORDER BY options.app_name
634 634 2.23 1199698393
SELECT loc.alias , loc.del , loc.l_addr1 , loc.l_addr2 , loc.l_a
ddr3 , loc.l_addr4 , loc.l_addr5 , loc.l_addr6 , loc.l_details ,
loc.l_name , loc.l_si_id , loc.last_mod , loc.persid , loc.z_cb
l1 , loc.zcb_l2 , loc.z_cb_l3 , loc.z_l_code , loc.z_ro_code ,
loc.z_zo_code FROM loc WHERE loc.id = :"SYS_B_0"
531 531 1.86 800192270
SELECT lrel.l_persid, lrel.l_attr, lrel.l_sql, lrel.r_persid, lr
el.r_attr, lrel.r_sql, lrel.id FROM lrel WHERE lrel.l_persid = :
"SYS_B_0" and lrel.l_attr = :"SYS_B_1" ORDER BY lrel.l_persid ,
lrel.l_attr , lrel.l_sql
438 438 1.54 1317334374
Select PROPERTY_NAME,PROPERTY_VALUE,PROPERTY_TYPE from CI_PROPER
TIES where PROPERTY_NAME=:"SYS_B_0"
429 429 1.51 1976028604
SQL ordered by Parse Calls for DB: AHD Instance: ahd Snaps: 20 -21
-> End Parse Calls Threshold: 1000
% Total
Parse Calls Executions Parses Hash Value
SELECT cr_stat.sym, cr_stat.code FROM cr_stat WHERE cr_stat.del
= :"SYS_B_0" ORDER BY cr_stat.sym
383 383 1.34 2599265718
DELETE FROM anima WHERE id = :"SYS_B_0"
359 359 1.26 1719939797
DELETE FROM att_evt WHERE id = :"SYS_B_0"
337 337 1.18 3069423312
SELECT anima.a_act , anima.a_delta , anima.a_lock , anima.a_name
, anima.a_org , anima.a_string , anima.a_time , anima.t_method
, anima.t_persid , anima.t_type FROM anima WHERE anima.id = :"SY
S_B_0"
330 332 1.16 1549656119
SELECT crsq.id FROM crsq WHERE crsq.code = :"SYS_B_0"
315 315 1.11 1734736338
UPDATE cr_prp SET last_mod_by = :"SYS_B_0" , last_mod_dt = :"SYS
_B_1" WHERE id = :"SYS_B_2"
308 308 1.08 618252548
SELECT cr_prp.sequence, cr_prp.id FROM cr_prp WHERE cr_prp.ownin
g_cr = :"SYS_B_0" ORDER BY cr_prp.sequence
277 277 0.97 321149819
INSERT INTO anima ( a_act, a_delta, a_lock, a_name, a_org, a_str
ing, a_time, t_method, t_persid, t_type, id ) VALUES ( :"SYS_B_
0" , :"SYS_B_1" , :"SYS_B_2" , :"SYS_B_3" , :"SYS_B_4" , nu
ll , :"SYS_B_5" , :"SYS_B_6" , :"SYS_B_7" , :"SYS_B_8" , :"
SYS_B_9" )
277 279 0.97 749386807
SELECT call_req.open_date, call_req.id FROM call_req WHERE call_
req.customer = :"SYS_B_0" AND call_req.active_flag = :"SYS_B_1"
ORDER BY call_req.open_date DESC
275 275 0.97 2816620377
INSERT INTO att_evt ( cancel_time, event_tmpl, fire_time, first_
fire_time, group_name, last_mod_dt, num_fire, obj_id, persid, st
art_time, status_flag, user_smag, wait_time, id ) VALUES ( null
, :"SYS_B_00" , :"SYS_B_01" , :"SYS_B_02" , :"SYS_B_03" ,
:"SYS_B_04" , :"SYS_B_05" , :"SYS_B_06" , :"SYS_B_07" , :"SY
269 269 0.94 3605948696
SELECT slatpl.del , slatpl.elapsed , slatpl.event , slatpl.last_
mod_by , slatpl.last_mod_dt , slatpl.object_type , slatpl.persid
, slatpl.service_type , slatpl.sym FROM slatpl WHERE slatpl.id
SQL ordered by Sharable Memory for DB: AHD Instance: ahd Snaps: 20 -21
-> End Sharable Memory Threshold: 1048576
Sharable Mem (b) Executions % Total Hash Value
23,912,520 231 13.6 139964375
SELECT anima.a_name, anima.t_persid, anima.t_method, anima.id FR
OM anima WHERE anima.t_persid LIKE :"SYS_B_0" ORDER BY anima.
a_name
18,314,292 26 10.4 380755726
SELECT call_req.open_date, call_req.id FROM call_req WHERE ( cal
l_req.ref_num LIKE :"SYS_B_00" ) AND ( call_req.group_id IN (
SELECT id FROM ctct WHERE id = :"SYS_B_01" OR id = :"SYS_B_02" O
R id = :"SYS_B_03" OR id = :"SYS_B_04" OR id = :"SYS_B_05" OR id
= :"SYS_B_06" OR id = :"SYS_B_07" OR id = :"SYS_B_08" OR id = :
12,365,844 107 7.0 1877135209
SELECT chg.open_date, chg.chg_ref_num, chg.id FROM chg WHERE ( c
hg.affected_contact = :"SYS_B_0" and chg.active_flag = :"SYS_B_1
" ) AND ( chg.affected_contact = :"SYS_B_2" ) ORDER BY chg.open
_date DESC
2,692,852 17 1.5 4181730075
SELECT ctct.c_last_name, ctct.c_first_name, ctct.c_middle_name,
ctct.c_public_phone, ctct.c_contact_num, ctct.c_org_id, ctct.c_l
_id, ctct.id FROM ctct, ct_ty WHERE ( ctct.c_last_name LIKE :"
SYS_B_0" AND ctct.c_ctp_id = ct_ty.id AND ct_ty.id = :"SYS_B_1"
AND ctct.del = :"SYS_B_2" AND ctct.id IN ( SELECT member FROM g
2,048,083 10 1.2 153455816
SELECT ctct.c_last_name, ctct.c_first_name, ctct.c_middle_name,
ctct.c_public_phone, ctct.c_contact_num, ctct.c_org_id, ctct.c_l
_id, ctct.id FROM ctct WHERE ( ctct.c_last_name LIKE :"SYS_B_0
" ) AND ( ( ctct.del = :"SYS_B_1" ) AND ( ctct.c_ctp_id = :"SYS_
B_2" AND ctct.alias = -:"SYS_B_3" ) ) ORDER BY ctct.c_last_name
1,653,628 3 0.9 1096419296
SELECT call_req.open_date, call_req.id FROM call_req WHERE ( cal
l_req.ref_num LIKE :"SYS_B_0" ) AND ( ( call_req.group_id IN (
SELECT group_id FROM grpmem WHERE member = :"SYS_B_1" ) ) or ca
ll_req.assignee = :"SYS_B_2" or call_req.customer = :"SYS_B_3" )
ORDER BY call_req.open_date DESC
SQL ordered by Version Count for DB: AHD Instance: ahd Snaps: 20 -21
-> End Version Count Threshold: 20
Version
Count Executions Hash Value
349 231 139964375
SELECT anima.a_name, anima.t_persid, anima.t_method, anima.id FR
OM anima WHERE anima.t_persid LIKE :"SYS_B_0" ORDER BY anima.
a_name
196 107 1877135209
SELECT chg.open_date, chg.chg_ref_num, chg.id FROM chg WHERE ( c
hg.affected_contact = :"SYS_B_0" and chg.active_flag = :"SYS_B_1
" ) AND ( chg.affected_contact = :"SYS_B_2" ) ORDER BY chg.open
_date DESC
127 26 380755726
SELECT call_req.open_date, call_req.id FROM call_req WHERE ( cal
l_req.ref_num LIKE :"SYS_B_00" ) AND ( call_req.group_id IN (
SELECT id FROM ctct WHERE id = :"SYS_B_01" OR id = :"SYS_B_02" O
R id = :"SYS_B_03" OR id = :"SYS_B_04" OR id = :"SYS_B_05" OR id
= :"SYS_B_06" OR id = :"SYS_B_07" OR id = :"SYS_B_08" OR id = :
36 17 4181730075
SELECT ctct.c_last_name, ctct.c_first_name, ctct.c_middle_name,
ctct.c_public_phone, ctct.c_contact_num, ctct.c_org_id, ctct.c_l
_id, ctct.id FROM ctct, ct_ty WHERE ( ctct.c_last_name LIKE :"
SYS_B_0" AND ctct.c_ctp_id = ct_ty.id AND ct_ty.id = :"SYS_B_1"
AND ctct.del = :"SYS_B_2" AND ctct.id IN ( SELECT member FROM g
33 10 153455816
SELECT ctct.c_last_name, ctct.c_first_name, ctct.c_middle_name,
ctct.c_public_phone, ctct.c_contact_num, ctct.c_org_id, ctct.c_l
_id, ctct.id FROM ctct WHERE ( ctct.c_last_name LIKE :"SYS_B_0
" ) AND ( ( ctct.del = :"SYS_B_1" ) AND ( ctct.c_ctp_id = :"SYS_
B_2" AND ctct.alias = -:"SYS_B_3" ) ) ORDER BY ctct.c_last_name
26 3 1096419296
SELECT call_req.open_date, call_req.id FROM call_req WHERE ( cal
l_req.ref_num LIKE :"SYS_B_0" ) AND ( ( call_req.group_id IN (
SELECT group_id FROM grpmem WHERE member = :"SYS_B_1" ) ) or ca
ll_req.assignee = :"SYS_B_2" or call_req.customer = :"SYS_B_3" )
ORDER BY call_req.open_date DESC
Instance Activity Stats for DB: AHD Instance: ahd Snaps: 20 -21
Statistic Total per Second per Trans
CPU used by this session 12,450 8.7 4.1
CPU used when call started 12,515 8.8 4.1
CR blocks created 53 0.0 0.0
DBWR buffers scanned 0 0.0 0.0
DBWR checkpoint buffers written 1,644 1.2 0.5
DBWR checkpoints 0 0.0 0.0
DBWR free buffers found 0 0.0 0.0
DBWR lru scans 0 0.0 0.0
DBWR make free requests 0 0.0 0.0
DBWR summed scan depth 0 0.0 0.0
DBWR transaction table writes 10 0.0 0.0
DBWR undo block writes 238 0.2 0.1
SQL*Net roundtrips to/from client 131,833 92.6 42.9
active txn count during cleanout 130 0.1 0.0
background checkpoints completed 0 0.0 0.0
background checkpoints started 0 0.0 0.0
background timeouts 2,161 1.5 0.7
branch node splits 0 0.0 0.0
buffer is not pinned count 3,147,925 2,210.6 1,024.1
buffer is pinned count 638,155 448.1 207.6
bytes received via SQL*Net from c 20,116,711 14,126.9 6,544.2
bytes sent via SQL*Net to client 33,961,169 23,849.1 11,047.9
calls to get snapshot scn: kcmgss 76,324 53.6 24.8
calls to kcmgas 6,266 4.4 2.0
calls to kcmgcs 110 0.1 0.0
change write time 25 0.0 0.0
cleanout - number of ktugct calls 145 0.1 0.1
cleanouts and rollbacks - consist 0 0.0 0.0
cleanouts only - consistent read 0 0.0 0.0
cluster key scan block gets 1,361 1.0 0.4
cluster key scans 1,146 0.8 0.4
commit cleanout failures: buffer 0 0.0 0.0
commit cleanout failures: callbac 3 0.0 0.0
commit cleanout failures: cannot 0 0.0 0.0
commit cleanouts 14,837 10.4 4.8
commit cleanouts successfully com 14,834 10.4 4.8
commit txn count during cleanout 106 0.1 0.0
consistent changes 2,123 1.5 0.7
consistent gets 3,336,864 2,343.3 1,085.5
consistent gets - examination 197,061 138.4 64.1
cursor authentications 71 0.1 0.0
data blocks consistent reads - un 2,123 1.5 0.7
db block changes 50,525 35.5 16.4
db block gets 47,774 33.6 15.5
deferred (CURRENT) block cleanout 7,940 5.6 2.6
dirty buffers inspected 0 0.0 0.0
enqueue conversions 29 0.0 0.0
enqueue releases 14,210 10.0 4.6
enqueue requests 14,210 10.0 4.6
enqueue waits 0 0.0 0.0
execute count 32,955 23.1 10.7
free buffer inspected 16 0.0 0.0
free buffer requested 140,283 98.5 45.6
hot buffers moved to head of LRU 950 0.7 0.3
immediate (CR) block cleanout app 0 0.0 0.0
immediate (CURRENT) block cleanou 2,804 2.0 0.9
Instance Activity Stats for DB: AHD Instance: ahd Snaps: 20 -21
Statistic Total per Second per Trans
index fast full scans (full) 157 0.1 0.1
index fetch by key 70,378 49.4 22.9
index scans kdiixs1 28,181 19.8 9.2
leaf node 90-10 splits 10 0.0 0.0
leaf node splits 76 0.1 0.0
logons cumulative 11 0.0 0.0
messages received 5,452 3.8 1.8
messages sent 5,452 3.8 1.8
no buffer to keep pinned count 0 0.0 0.0
no work - consistent read gets 3,085,481 2,166.8 1,003.7
opened cursors cumulative 4,561 3.2 1.5
parse count (failures) 0 0.0 0.0
parse count (hard) 412 0.3 0.1
parse count (total) 28,484 20.0 9.3
parse time cpu 426 0.3 0.1
parse time elapsed 469 0.3 0.2
physical reads 138,930 97.6 45.2
physical reads direct 0 0.0 0.0
physical writes 1,644 1.2 0.5
physical writes direct 0 0.0 0.0
physical writes non checkpoint 232 0.2 0.1
pinned buffers inspected 7 0.0 0.0
prefetched blocks 32,732 23.0 10.7
process last non-idle time 12,884,949,552 9,048,419.6 4,191,590.6
recursive calls 22,718 16.0 7.4
recursive cpu usage 226 0.2 0.1
redo blocks written 19,178 13.5 6.2
redo buffer allocation retries 0 0.0 0.0
redo entries 27,265 19.2 8.9
redo log space requests 0 0.0 0.0
redo log space wait time 0 0.0 0.0
redo size 8,488,216 5,960.8 2,761.3
redo synch time 74 0.1 0.0
redo synch writes 3,078 2.2 1.0
redo wastage 1,040,788 730.9 338.6
redo write time 75 0.1 0.0
redo writer latching time 0 0.0 0.0
redo writes 5,216 3.7 1.7
rollback changes - undo records a 6 0.0 0.0
rollbacks only - consistent read 233 0.2 0.1
rows fetched via callback 54,581 38.3 17.8
session connect time 12,884,949,552 9,048,419.6 4,191,590.6
session logical reads 3,384,638 2,376.9 1,101.1
session pga memory max 6,168,536 4,331.8 2,006.7
session uga memory 599,984 421.3 195.2
session uga memory max 9,592,864 6,736.6 3,120.7
shared hash latch upgrades - no w 27,737 19.5 9.0
shared hash latch upgrades - wait 84 0.1 0.0
sorts (disk) 0 0.0 0.0
sorts (memory) 6,834 4.8 2.2
sorts (rows) 3,229,994 2,268.3 1,050.8
summed dirty queue length 0 0.0 0.0
switch current to new buffer 990 0.7 0.3
table fetch by rowid 474,673 333.3 154.4
table fetch continued row 8 0.0 0.0
table scan blocks gotten 2,751,375 1,932.2 895.1
Instance Activity Stats for DB: AHD Instance: ahd Snaps: 20 -21
Statistic Total per Second per Trans
table scan rows gotten 55,928,200 39,275.4 18,194.0
table scans (long tables) 245 0.2 0.1
table scans (short tables) 3,383 2.4 1.1
transaction rollbacks 3 0.0 0.0
transaction tables consistent rea 0 0.0 0.0
transaction tables consistent rea 0 0.0 0.0
user calls 131,904 92.6 42.9
user commits 3,074 2.2 1.0
user rollbacks 0 0.0 0.0
workarea executions - onepass 0 0.0 0.0
workarea executions - optimal 8,438 5.9 2.7
write clones created in backgroun 0 0.0 0.0
write clones created in foregroun 0 0.0 0.0
Tablespace IO Stats for DB: AHD Instance: ahd Snaps: 20 -21
->ordered by IOs (Reads + Writes) desc
Tablespace
Av Av Av Av Buffer Av Buf
Reads Reads/s Rd(ms) Blks/Rd Writes Writes/s Waits Wt(ms)
AHD1_DATA
105,869 74 0.9 1.3 828 1 11,740 0.5
AHD1_IDX
38 0 7.4 1.0 563 0 0 0.0
PERFSTAT
372 0 3.6 1.0 0 0 0 0.0
UNDOTBS1
0 0 0.0 248 0 0 0.0
SYSTEM
6 0 6.7 1.0 5 0 0 0.0
File IO Stats for DB: AHD Instance: ahd Snaps: 20 -21
->ordered by Tablespace, File
Tablespace Filename
Av Av Av Av Buffer Av Buf
Reads Reads/s Rd(ms) Blks/Rd Writes Writes/s Waits Wt(ms)
AHD1_DATA E:\ORACLE\ORADATA\AHD\AHD1_DATA.ORA
53,454 38 0.9 1.3 432 0 5,949 0.5
E:\ORACLE\ORADATA\AHD\AHD2_DATA.ORA
52,415 37 0.9 1.3 396 0 5,791 0.5
AHD1_IDX E:\ORACLE\ORADATA\AHD\AHD1_IDX.ORA
38 0 7.4 1.0 563 0 0
PERFSTAT E:\ORACLE\ORADATA\AHD\PERFSTAT.ORA
372 0 3.6 1.0 0 0 0
SYSTEM E:\ORACLE\ORADATA\AHD\SYSTEM01.DBF
6 0 6.7 1.0 5 0 0
UNDOTBS1 E:\ORACLE\ORADATA\AHD\UNDOTBS01.DBF
0 0 248 0 0
Buffer Pool Statistics for DB: AHD Instance: ahd Snaps: 20 -21
-> Standard block size Pools D: default, K: keep, R: recycle
-> Default Pools for other block sizes: 2k, 4k, 8k, 16k, 32k
Free Write Buffer
Number of Cache Buffer Physical Physical Buffer Complete Busy
P Buffers Hit % Gets Reads Writes Waits Waits Waits
D 82,082 97.8 6,327,007 138,971 1,644 0 0 11,760
Instance Recovery Stats for DB: AHD Instance: ahd Snaps: 20 -21
-> B: Begin snapshot, E: End snapshot
Targt Estd Log File Log Ckpt Log Ckpt
MTTR MTTR Recovery Actual Target Size Timeout Interval
(s) (s) Estd IOs Redo Blks Redo Blks Redo Blks Redo Blks Redo Blks
B 75 26 2354 18057 17632 184320 17632
E 75 27 2967 23569 22952 184320 22952
Buffer Pool Advisory for DB: AHD Instance: ahd End Snap: 21
-> Only rows with estimated physical reads >0 are displayed
-> ordered by Block Size, Buffers For Estimate
Size for Size Buffers for Est Physical Estimated
P Estimate (M) Factr Estimate Read Factor Physical Reads
D 64 .1 8,008 261.38 4,357,231,706
D 128 .2 16,016 207.44 3,458,029,385
D 192 .3 24,024 143.22 2,387,570,894
D 256 .4 32,032 2.29 38,243,018
D 320 .5 40,040 1.89 31,541,321
D 384 .6 48,048 1.74 29,023,767
D 448 .7 56,056 1.69 28,232,064
D 512 .8 64,064 1.20 19,951,481
D 576 .9 72,072 1.11 18,529,925
D 640 1.0 80,080 1.04 17,367,752
D 656 1.0 82,082 1.00 16,670,129
D 704 1.1 88,088 0.97 16,124,256
D 768 1.2 96,096 0.91 15,155,822
D 832 1.3 104,104 0.90 15,055,099
D 896 1.4 112,112 0.89 14,839,567
D 960 1.5 120,120 0.88 14,668,682
D 1,024 1.6 128,128 0.87 14,479,726
D 1,088 1.7 136,136 0.84 13,988,866
D 1,152 1.8 144,144 0.70 11,723,518
D 1,216 1.9 152,152 0.61 10,156,857
D 1,280 2.0 160,160 0.20 3,281,883
Buffer wait Statistics for DB: AHD Instance: ahd Snaps: 20 -21
-> ordered by wait time desc, waits desc
Tot Wait Avg
Class Waits Time (s) Time (ms)
data block 11,754 6 0
PGA Aggr Target Stats for DB: AHD Instance: ahd Snaps: 20 -21
-> B: Begin snap E: End snap (rows dentified with B or E contain data
which is absolute i.e. not diffed over the interval)
-> PGA cache hit % - percentage of W/A (WorkArea) data processed only in-memory
-> Auto PGA Target - actual workarea memory target
-> W/A PGA Used - amount of memory used for all Workareas (manual + auto)
-> %PGA W/A Mem - percentage of PGA memory allocated to workareas
-> %Auto W/A Mem - percentage of workarea memory controlled by Auto Mem Mgmt
-> %Man W/A Mem - percentage of workarea memory under manual control
PGA Cache Hit % W/A MB Processed Extra W/A MB Read/Written
100.0 1,169 0
%PGA %Auto %Man
PGA Aggr Auto PGA PGA Mem W/A PGA W/A W/A W/A Global Mem
Target(M) Target(M) Alloc(M) Used(M) Mem Mem Mem Bound(K)
B 350 293 37.6 0.0 .0 .0 .0 17,920
E 350 293 37.5 0.2 .6 100.0 .0 17,920
PGA Aggr Target Histogram for DB: AHD Instance: ahd Snaps: 20 -21
-> Optimal Executions are purely in-memory operations
Low High
Optimal Optimal Total Execs Optimal Execs 1-Pass Execs M-Pass Execs
8K 16K 6,809 6,809 0 0
16K 32K 148 148 0 0
32K 64K 90 90 0 0
64K 128K 154 154 0 0
128K 256K 73 73 0 0
256K 512K 308 308 0 0
512K 1024K 374 374 0 0
1M 2M 171 171 0 0
2M 4M 217 217 0 0
4M 8M 10 10 0 0
PGA Memory Advisory for DB: AHD Instance: ahd End Snap: 21
-> When using Auto Memory Mgmt, minimally choose a pga_aggregate_target value
where Estd PGA Overalloc Count is 0
Estd Extra Estd PGA Estd PGA
PGA Target Size W/A MB W/A MB Read/ Cache Overalloc
Est (MB) Factr Processed Written to Disk Hit % Count
44 0.1 180,060.5 42,218.7 81.0 4
88 0.3 180,060.5 23,194.7 89.0 0
175 0.5 180,060.5 9,436.8 95.0 0
263 0.8 180,060.5 9,356.7 95.0 0
350 1.0 180,060.5 9,274.8 95.0 0
420 1.2 180,060.5 9,169.9 95.0 0
490 1.4 180,060.5 9,148.0 95.0 0
560 1.6 180,060.5 9,148.0 95.0 0
630 1.8 180,060.5 9,148.0 95.0 0
700 2.0 180,060.5 9,148.0 95.0 0
1,050 3.0 180,060.5 9,148.0 95.0 0
1,400 4.0 180,060.5 9,148.0 95.0 0
2,100 6.0 180,060.5 3,983.3 98.0 0
2,800 8.0 180,060.5 3,983.3 98.0 0
Rollback Segment Stats for DB: AHD Instance: ahd Snaps: 20 -21
->A high value for "Pct Waits" suggests more rollback segments may be required
->RBS stats may not be accurate between begin and end snaps when using Auto Undo
managment, as RBS may be dynamically created and dropped as needed
Trans Table Pct Undo Bytes
RBS No Gets Waits Written Wraps Shrinks Extends
0 29.0 0.00 0 0 0 0
1 975.0 0.00 122,796 0 0 0
2 1,244.0 0.00 1,094,706 10 0 5
3 816.0 0.00 118,596 0 0 0
4 1,430.0 0.00 212,754 2 0 0
5 1,716.0 0.00 291,940 2 0 0
6 1,287.0 0.00 197,900 0 0 0
7 1,674.0 0.00 279,160 0 0 0
8 1,031.0 0.00 148,216 0 0 0
9 947.0 0.00 141,870 0 0 0
10 834.0 0.00 117,422 0 0 0
Rollback Segment Storage for DB: AHD Instance: ahd Snaps: 20 -21
->Optimal Size should be larger than Avg Active
RBS No Segment Size Avg Active Optimal Size Maximum Size
0 385,024 0 385,024
1 2,220,032 455,412 2,220,032
2 2,088,960 333,026 2,220,032
3 2,220,032 456,101 2,220,032
4 2,220,032 474,584 3,268,608
5 2,220,032 480,865 3,268,608
6 2,220,032 513,967 3,268,608
7 2,220,032 480,785 2,220,032
8 2,220,032 496,182 2,220,032
9 2,220,032 486,763 2,220,032
10 2,220,032 430,016 6,414,336
Undo Segment Summary for DB: AHD Instance: ahd Snaps: 20 -21
-> Undo segment block stats:
-> uS - unexpired Stolen, uR - unexpired Released, uU - unexpired reUsed
-> eS - expired Stolen, eR - expired Released, eU - expired reUsed
Undo Undo Num Max Qry Max Tx Snapshot Out of uS/uR/uU/
TS# Blocks Trans Len (s) Concurcy Too Old Space eS/eR/eU
1 395 2,900,725 5 1 0 0 0/0/0/0/0/0
Undo Segment Stats for DB: AHD Instance: ahd Snaps: 20 -21
-> ordered by Time desc
Undo Num Max Qry Max Tx Snap Out of uS/uR/uU/
End Time Blocks Trans Len (s) Concy Too Old Space eS/eR/eU
13-Feb 15:04 96 ######## 4 1 0 0 0/0/0/0/0/0
13-Feb 14:54 299 ######## 5 1 0 0 0/0/0/0/0/0
Latch Activity for DB: AHD Instance: ahd Snaps: 20 -21
->"Get Requests", "Pct Get Miss" and "Avg Slps/Miss" are statistics for
willing-to-wait latch get requests
->"NoWait Requests", "Pct NoWait Miss" are for no-wait latch get requests
->"Pct Misses" for both should be very close to 0.0
Pct Avg Wait Pct
Get Get Slps Time NoWait NoWait
Latch Requests Miss /Miss (s) Requests Miss
Consistent RBA 5,216 0.0 0 0
FOB s.o list latch 34 0.0 0 0
SQL memory manager latch 1 0.0 0 462 0.0
SQL memory manager worka 40,347 0.0 0 0
active checkpoint queue 1,261 0.0 0 0
archive control 163 0.0 0 0
archive process latch 29 0.0 0 0
cache buffer handles 378 0.0 0 0
cache buffers chains 6,836,244 0.4 0.0 0 266,617 0.0
cache buffers lru chain 244,157 0.0 0.0 0 140,432 0.0
channel handle pool latc 21 0.0 0 0
channel operations paren 960 0.0 0 0
checkpoint queue latch 86,982 0.0 0 2,337 0.0
child cursor hash table 6,464 0.0 0.0 0 0
dml lock allocation 15,005 0.0 0 0
dummy allocation 21 0.0 0 0
enqueue hash chains 28,447 0.0 0 0
enqueues 8,689 0.0 0 0
event group latch 11 0.0 0 0
file number translation 4,079 0.0 0 0
hash table column usage 38 0.0 0 187,596 0.0
hash table modification 1 0.0 0 0
job_queue_processes para 23 0.0 0 0
ktm global data 4 0.0 0 0
kwqit: protect wakeup ti 45 0.0 0 0
lgwr LWN SCN 5,328 0.4 0.0 0 0
library cache 342,865 0.2 0.0 0 342 0.6
library cache load lock 452 0.0 0 0
library cache pin 197,662 0.0 0.0 0 0
library cache pin alloca 124,035 0.0 0.0 0 0
list of block allocation 55 0.0 0 0
messages 30,779 0.0 0.0 0 0
mostly latch-free SCN 5,459 1.8 0.0 0 0
multiblock read objects 194,822 0.0 0.0 0 0
ncodef allocation latch 23 0.0 0 0
object stats modificatio 618 0.0 0 0
post/wait queue 10,441 0.0 0 3,078 0.0
process allocation 11 0.0 0 11 0.0
process group creation 21 0.0 0 0
redo allocation 37,773 0.0 0.0 0 0
redo copy 0 0 27,274 0.0
redo writing 17,880 0.0 0 0
row cache enqueue latch 169,423 0.0 0.0 0 0
row cache objects 169,795 0.0 0 3 0.0
sequence cache 38 0.0 0 0
session allocation 15,580 0.0 0 0
session idle bit 269,419 0.0 0.0 0 0
session switching 23 0.0 0 0
session timer 478 0.0 0 0
shared pool 104,427 0.1 0.0 0 0
Latch Activity for DB: AHD Instance: ahd Snaps: 20 -21
->"Get Requests", "Pct Get Miss" and "Avg Slps/Miss" are statistics for
willing-to-wait latch get requests
->"NoWait Requests", "Pct NoWait Miss" are for no-wait latch get requests
->"Pct Misses" for both should be very close to 0.0
Pct Avg Wait Pct
Get Get Slps Time NoWait NoWait
Latch Requests Miss /Miss (s) Requests Miss
sim partition latch 0 0 32 0.0
simulator hash latch 217,119 0.0 0.0 0 0
simulator lru latch 16,247 0.0 0 902 0.4
sort extent pool 29 0.0 0 0
transaction allocation 36 0.0 0 0
transaction branch alloc 23 0.0 0 0
undo global data 19,973 0.0 0 0
user lock 42 0.0 0 0
Latch Sleep breakdown for DB: AHD Instance: ahd Snaps: 20 -21
-> ordered by misses desc
Get Spin &
Latch Name Requests Misses Sleeps Sleeps 1->4
cache buffers chains 6,836,244 26,201 46 0/0/0/0/0
library cache 342,865 778 5 773/5/0/0/0
shared pool 104,427 125 3 122/3/0/0/0
Latch Miss Sources for DB: AHD Instance: ahd Snaps: 20 -21
-> only latches with sleeps are shown
-> ordered by name, sleeps desc
NoWait Waiter
Latch Name Where Misses Sleeps Sleeps
cache buffers chains kcbgtcr: kslbegin excl 0 32 30
cache buffers chains kcbrls: kslbegin 0 7 13
cache buffers chains kcbzwb 0 4 3
cache buffers chains kcbgtcr: fast path 0 3 0
library cache kglic 0 2 0
library cache kglobpn: child: 0 2 0
library cache kgllkdl: child: cleanup 0 1 0
shared pool kghalo 0 2 0
shared pool kghalp 0 1 0
Child Latch Statistics DB: AHD Instance: ahd Snaps: 20 -21
-> only latches with sleeps/gets > 1/100000 are shown
-> ordered by name, gets desc
Child Get Spin &
Latch Name Num Requests Misses Sleeps Sleeps 1->4
cache buffers chains 439 28,269 1,276 1 0/0/0/0/0
cache buffers chains 269 26,297 842 1 0/0/0/0/0
cache buffers chains 1010 17,482 49 2 0/0/0/0/0
cache buffers chains 260 11,141 20 1 0/0/0/0/0
cache buffers chains 324 9,454 29 1 0/0/0/0/0
cache buffers chains 840 7,235 20 1 0/0/0/0/0
cache buffers chains 46 6,868 25 1 0/0/0/0/0
cache buffers chains 835 6,799 26 2 0/0/0/0/0
cache buffers chains 202 6,768 17 1 0/0/0/0/0
cache buffers chains 740 6,573 38 2 0/0/0/0/0
cache buffers chains 592 6,508 30 1 0/0/0/0/0
cache buffers chains 436 6,485 25 2 0/0/0/0/0
cache buffers chains 513 6,443 16 1 0/0/0/0/0
cache buffers chains 844 6,436 28 1 0/0/0/0/0
cache buffers chains 117 6,423 25 1 0/0/0/0/0
cache buffers chains 389 6,381 25 1 0/0/0/0/0
cache buffers chains 116 6,349 29 1 0/0/0/0/0
cache buffers chains 51 6,340 34 1 0/0/0/0/0
cache buffers chains 914 6,259 31 1 0/0/0/0/0
cache buffers chains 713 6,249 24 1 0/0/0/0/0
cache buffers chains 465 6,198 27 2 0/0/0/0/0
cache buffers chains 416 6,193 27 1 0/0/0/0/0
cache buffers chains 432 6,155 34 1 0/0/0/0/0
cache buffers chains 583 6,152 23 2 0/0/0/0/0
cache buffers chains 126 6,147 35 1 0/0/0/0/0
cache buffers chains 879 6,043 21 1 0/0/0/0/0
cache buffers chains 110 6,010 25 1 0/0/0/0/0
cache buffers chains 138 6,010 25 1 0/0/0/0/0
cache buffers chains 472 6,002 31 1 0/0/0/0/0
cache buffers chains 908 5,964 20 1 0/0/0/0/0
cache buffers chains 860 5,950 23 1 0/0/0/0/0
cache buffers chains 71 5,945 29 3 0/0/0/0/0
cache buffers chains 20 5,780 28 1 0/0/0/0/0
cache buffers chains 932 5,759 25 1 0/0/0/0/0
cache buffers chains 866 5,610 22 1 0/0/0/0/0
cache buffers chains 989 5,454 34 2 0/0/0/0/0
cache buffers chains 1005 5,434 40 1 0/0/0/0/0
library cache 6 47,067 52 3 49/3/0/0/0
shared pool 1 99,771 124 3 121/3/0/0/0
Top 5 Logical Reads per Segment for DB: AHD Instance: ahd Snaps: 20 -21
-> End Segment Logical Reads Threshold: 10000
Subobject Obj. Logical
Owner Tablespace Object Name Name Type Reads %Total
AHD AHD1_DATA CALL_REQ TABLE 1,714,928 51.19
AHD AHD1_DATA CTCT TABLE 1,169,360 34.90
AHD AHD1_IDX SYS_C003707 INDEX 89,152 2.66
AHD AHD1_DATA CNOTE TABLE 66,272 1.98
AHD AHD1_IDX CALL_REQ_X5 INDEX 61,360 1.83
Top 5 Physical Reads per Segment for DB: AHD Instance: ahd Snaps: 20 -21
-> End Segment Physical Reads Threshold: 1000
Subobject Obj. Physical
Owner Tablespace Object Name Name Type Reads %Total
AHD AHD1_DATA CALL_REQ TABLE 132,989 95.95
AHD AHD1_DATA CTCT TABLE 5,325 3.84
AHD AHD1_DATA CI_AUDIT_TRAILS_GU_I INDEX 43 .03
AHD AHD1_DATA ACT_LOG TABLE 38 .03
AHD AHD1_DATA CI_EXT_CALLS_GUID INDEX 36 .03
Top 5 Buf. Busy Waits per Segment for DB: AHD Instance: ahd Snaps: 20 -21
-> End Segment Buffer Busy Waits Threshold: 100
Buffer
Subobject Obj. Busy
Owner Tablespace Object Name Name Type Waits %Total
AHD AHD1_DATA CALL_REQ TABLE 11,751 99.95
AHD AHD1_DATA CTCT TABLE 6 .05
Dictionary Cache Stats for DB: AHD Instance: ahd Snaps: 20 -21
->"Pct Misses" should be very low (< 2% in most cases)
->"Cache Usage" is the number of cache entries being used
->"Pct SGA" is the ratio of usage to allocated size for that cache
Get Pct Scan Pct Mod Final
Cache Requests Miss Reqs Miss Reqs Usage
dc_files 30 0.0 0 0 15
dc_histogram_defs 3,022 3.9 0 0 1,919
dc_object_ids 22,961 0.1 0 0 1,181
dc_objects 1,092 9.2 0 0 1,026
dc_profiles 11 0.0 0 0 1
dc_rollback_segments 168 0.0 0 0 22
dc_segments 5,519 0.1 0 0 1,334
dc_sequences 1 0.0 0 1 2
dc_tablespace_quotas 3 0.0 0 3 2
dc_tablespaces 25,902 0.0 0 0 16
dc_user_grants 127 0.0 0 0 22
dc_usernames 110 0.0 0 0 18
dc_users 26,077 0.0 0 0 30
Library Cache Activity for DB: AHD Instance: ahd Snaps: 20 -21
->"Pct Misses" should be very low
Get Pct Pin Pct Invali-
Namespace Requests Miss Requests Miss Reloads dations
CLUSTER 19 0.0 16 0.0 0 0
INDEX 315 0.0 315 0.0 0 0
SQL AREA 27,908 0.0 94,300 0.5 38 0
TABLE/PROCEDURE 3,793 2.6 6,017 6.5 55 0
TRIGGER 20 0.0 20 0.0 0 0
Shared Pool Advisory for DB: AHD Instance: ahd End Snap: 21
-> Note there is often a 1:Many correlation between a single logical object
in the Library Cache, and the physical number of memory objects associated
with it. Therefore comparing the number of Lib Cache objects (e.g. in
v$librarycache), with the number of Lib Cache Memory Objects is invalid
Estd
Shared Pool SP Estd Estd Estd Lib LC Time
Size for Size Lib Cache Lib Cache Cache Time Saved Estd Lib Cache
Estim (M) Factr Size (M) Mem Obj Saved (s) Factr Mem Obj Hits
88 .6 81 11,169 59,229 1.0 6,202,663
104 .7 96 13,308 59,237 1.0 6,207,373
120 .8 112 15,603 59,277 1.0 6,228,405
136 .9 127 18,086 59,348 1.0 6,265,370
152 1.0 142 19,501 59,379 1.0 6,295,279
168 1.1 157 21,035 59,426 1.0 6,314,861
184 1.2 172 22,038 59,455 1.0 6,325,903
200 1.3 187 23,807 59,459 1.0 6,328,446
216 1.4 202 25,911 59,460 1.0 6,329,386
232 1.5 217 28,194 59,461 1.0 6,330,245
248 1.6 232 29,884 59,462 1.0 6,330,914
264 1.7 248 31,127 59,462 1.0 6,331,222
280 1.8 263 32,878 59,463 1.0 6,331,563
296 1.9 278 34,121 59,463 1.0 6,331,898
312 2.1 295 36,139 59,463 1.0 6,332,102
SGA Memory Summary for DB: AHD Instance: ahd Snaps: 20 -21
SGA regions Size in Bytes
Database Buffers 687,865,856
Fixed Size 455,196
Redo Buffers 929,792
Variable Size 293,601,280
sum 982,852,124
SGA breakdown difference for DB: AHD Instance: ahd Snaps: 20 -21
Pool Name Begin value End value % Diff
java free memory 75,497,472 75,497,472 0.00
large free memory 41,943,040 41,943,040 0.00
shared 1M buffer 2,098,176 2,098,176 0.00
shared Checkpoint queue 846,912 846,912 0.00
shared FileOpenBlock 695,504 695,504 0.00
shared KGK heap 3,756 3,756 0.00
shared KGLS heap 1,230,944 1,438,740 16.88
shared KQR L PO 2,064 2,064 0.00
shared KQR M PO 2,480,924 2,514,220 1.34
shared KQR S PO 383,036 383,036 0.00
shared KQR S SO 5,636 5,636 0.00
shared KSXR pending messages que 841,036 841,036 0.00
shared KSXR receive buffers 1,033,000 1,033,000 0.00
shared MTTR advisory 97,412 97,412 0.00
shared PL/SQL DIANA 624,112 624,112 0.00
shared PL/SQL MPCODE 422,640 422,640 0.00
shared PLS non-lib hp 2,068 2,068 0.00
shared character set object 323,724 323,724 0.00
shared dictionary cache 1,610,880 1,610,880 0.00
shared errors 35,964 35,964 0.00
shared event statistics per sess 1,718,360 1,718,360 0.00
shared fixed allocation callback 300 300 0.00
shared free memory 26,982,004 26,841,956 -0.52
shared joxs heap init 4,220 4,220 0.00
shared kgl simulator 3,980,240 3,996,976 0.42
shared library cache 54,425,164 53,999,624 -0.78
shared message pool freequeue 834,752 834,752 0.00
shared miscellaneous 8,126,704 8,177,516 0.63
shared parameters 1,632 1,632 0.00
shared sessions 410,720 410,720 0.00
shared sim memory hea 377,656 377,656 0.00
shared sql area 66,513,080 66,768,476 0.38
shared subheap 45,216 45,216 0.00
shared table definiti 1,200 2,752 129.33
shared trigger defini 340 340 0.00
shared trigger inform 1,292 1,292 0.00
shared trigger source 100 100 0.00
buffer_cache 687,865,856 687,865,856 0.00
fixed_sga 455,196 455,196 0.00
log_buffer 918,528 918,528 0.00
init.ora Parameters for DB: AHD Instance: ahd Snaps: 20 -21
End value
Parameter Name Begin value (if different)
aq_tm_processes 1
background_dump_dest E:\oracle\admin\ahd\bdump
compatible 9.2.0.0.0
control_files E:\oracle\oradata\ahd\CONTROL01.C
core_dump_dest E:\oracle\admin\ahd\cdump
cursor_sharing SIMILAR
db_block_size 8192
db_cache_size 687865856
db_domain
db_file_multiblock_read_count 8
db_name ahd
db_writer_processes 2
dispatchers (PROTOCOL=TCP) (SERVICE=ahdXDB)
fast_start_mttr_target 300
hash_join_enabled TRUE
instance_name ahd
java_pool_size 75497472
job_queue_processes 10
large_pool_size 41943040
log_archive_dest_1 location=c:\archive
log_archive_format arc%d_%t_%s.arc
log_archive_start TRUE
open_cursors 300
pga_aggregate_target 367001600
processes 150
query_rewrite_enabled FALSE
remote_login_passwordfile EXCLUSIVE
shared_pool_size 159383552
sort_area_size 10485760
star_transformation_enabled FALSE
timed_statistics TRUE
undo_management AUTO
undo_retention 3600
undo_tablespace UNDOTBS1
user_dump_dest E:\oracle\admin\ahd\udump
End of ReportI am getting buffer busy waits on some tables.
Users are not experiencing any problem.Looks like you got bit by the CTD troll while sleeping.
Note also that (if I'm reading the report alright) out of 23 mins you have 6 seconds accounted to buffer busy waits.
Read the sample chapter here. -
Difference between wait events 'buffer busy waits' & 'latch: CBC'
Hi ,
Can some one explain me the Difference Between 'Buffer Busy Waits' and 'Latch: Cache Buffers Chains"? What was explained in metalink note Doc ID: 833303.1
, is incomprehensible to me.
Looking for easy and better explanation.
Thanks
NaveenNaveen Sangam wrote:
Can some one explain me the Difference Between 'Buffer Busy Waits' and 'Latch: Cache Buffers Chains"? What was explained in metalink note Doc ID: 833303.1
, is incomprehensible to me.
That note is awful and should be witdrawn - amongst other things it makes it sound as if there is only one reason for buffer busy waits. There is an option to comment on such notes - I suggest you use it.
Going back a little further from Aman's description - and ignoring some of the internal details:
The buffer cache is split into a large number of small groups of buffered blocks; these groups are usually called "hash buckets" or "hash chains". If you need to find a block and it is buffered, Oracle can do some hashing arithmetic to work out which chain the block will be in.
The chains are protected by latches (typically a single latch protects 64 - 128 chains). You cannot examine a chain unless you are able to get the latch that protects it. So the commonest action you go through to view or modify a buffered block is:
<ul>
work out which chain
get the latch for the chain xxx
search along the chain to see if the block is in memory
attach a "pin" to the buffered block block if you find it (to make sure it can't be kicked out of memory)
release the latch
do what you want to do with the buffered block ***
get the latch for the chain xxx
remove the pin from the buffered block
release the latch
</ul>
The two points marked xxx are where you might end up sleeping in a wait for the "cache buffers chains latch". If too many people try to get the latch at the same time some of them will eventually fail and go to sleep for a short period.
The point marked *** is where you get the buffer busy wait. When you attach the pin to the buffered block it's possible that what you want to do to the bllock is incompatible with what other people are already doing - so you have to attach your pin to the "waiters" list (the people currently using the block will have their pins attached to the "users" list". Eventually your wait will time out, or the users will get out of the way and you can move your pin to the users list and do whatever it was you wanted to do.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk
To post code, statspack/AWR report, execution plans or trace files, start and end the section with the tag {noformat}{noformat} (lowercase, curly brackets, no spaces) so that the text appears in fixed format.
"Science is more than a body of knowledge; it is a way of thinking"
Carl Sagan -
Id column in gc buffer busy waits
Hello,
What's the id column show for gc buffer busy or gc current request waits.. I could not find any description for "gc current request". However, Here is what I found in oracle doc .. It's not so clear..
Parameter Description
file# See "file#" on page C-3
block# See "block#" on page C-2
id The buffer busy wait event is called from different places in the sessionThanksAny one??
-
Statspack interpreting help - buffer busy waits
Hi,
I've got statspack report from 9.2.0.8 DB, cpu_count = 12 , there is 'buffer busy waits' in top 5 .
Is there a problem ?
DB Name DB Id Instance Inst Num Release Cluster Host
XXXX 138180125 XXXX 1 9.2.0.8.0 NO X1
Snap Id Snap Time Sessions Curs/Sess Comment
Begin Snap: 35980 14-Jul-10 01:00:02 17 8.8
End Snap: 35984 14-Jul-10 05:00:01 17 8.8
Elapsed: 239.98 (mins)
Cache Sizes (end)
~~~~~~~~~~~~~~~~~
Buffer Cache: 3,072M Std Block Size: 8K
Shared Pool Size: 512M Log Buffer: 4,096K
Load Profile
~~~~~~~~~~~~ Per Second Per Transaction
Redo size: 317,746.23 4,498.59
Logical reads: 11,150.77 157.87
Block changes: 2,134.89 30.23
Physical reads: 466.05 6.60
Physical writes: 133.62 1.89
User calls: 82.42 1.17
Parses: 67.92 0.96
Hard parses: 0.02 0.00
Sorts: 106.77 1.51
Logons: 0.03 0.00
Executes: 516.58 7.31
Transactions: 70.63
% Blocks changed per Read: 19.15 Recursive Call %: 95.00
Rollback per transaction %: 0.00 Rows per Sort: 4.34
Instance Efficiency Percentages (Target 100%)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Buffer Nowait %: 99.03 Redo NoWait %: 100.00
Buffer Hit %: 95.91 In-memory Sort %: 100.00
Library Hit %: 100.00 Soft Parse %: 99.98
Execute to Parse %: 86.85 Latch Hit %: 99.65
Parse CPU to Parse Elapsd %: 7.82 % Non-Parse CPU: 99.91
Shared Pool Statistics Begin End
Memory Usage %: 43.53 43.92
% SQL with executions>1: 64.89 70.00
% Memory for SQL w/exec>1: 55.95 61.64
Top 5 Timed Events
~~~~~~~~~~~~~~~~~~ % Total
Event Waits Time (s) Ela Time
SQL*Net message from dblink 797,760 44,575 41.69
PL/SQL lock timer 1,207 34,992 32.73
db file sequential read 3,297,249 17,047 15.94
buffer busy waits 1,558,995 3,987 3.73
CPU time 3,204 3.00
Statistic Total per Second per Trans
enqueue timeouts 299 0.0 0.0
enqueue waits 425 0.0 0.0
exchange deadlocks 41 0.0 0.0
execute count 7,438,297 516.6 7.3
failed probes on index block recl 13 0.0 0.0
free buffer inspected 107,385 7.5 0.1
free buffer requested 7,344,870 510.1 7.2
hot buffers moved to head of LRU 2,332,802 162.0 2.3
immediate (CR) block cleanout app 356,492 24.8 0.4
immediate (CURRENT) block cleanou 1,751,731 121.7 1.7
index crx upgrade (found) 7 0.0 0.0
index crx upgrade (positioned) 25,604 1.8 0.0
index fast full scans (full) 888 0.1 0.0
index fetch by key 6,008,269 417.3 5.9
index scans kdiixs1 2,343,163 162.7 2.3
leaf node 90-10 splits 330 0.0 0.0
leaf node splits 13,681 1.0 0.0
logons cumulative 447 0.0 0.0
messages received 2,760,503 191.7 2.7
messages sent 2,760,503 191.7 2.7
no buffer to keep pinned count 0 0.0 0.0
no work - consistent read gets 89,143,249 6,190.9 87.7
opened cursors cumulative 978,462 68.0 1.0
parse count (failures) 0 0.0 0.0
parse count (hard) 243 0.0 0.0
parse count (total) 977,939 67.9 1.0
parse time cpu 276 0.0 0.0
parse time elapsed 3,531 0.3 0.0
physical reads 6,710,684 466.1 6.6
physical reads direct 140,520 9.8 0.1
physical writes 1,924,011 133.6 1.9
physical writes direct 149,434 10.4 0.2
physical writes non checkpoint 1,160,293 80.6 1.1
pinned buffers inspected 88,165 6.1 0.1
prefetched blocks 2,965,135 205.9 2.9
prefetched blocks aged out before 1,485 0.1 0.0
process last non-idle time 14,401 1.0 0.0
recovery blocks read 0 0.0 0.0
recursive calls 22,566,381 1,567.2 22.2
recursive cpu usage 314,662 21.9 0.3
redo blocks written 9,712,190 674.5 9.6
redo buffer allocation retries 483 0.0 0.0
redo entries 17,147,344 1,190.9 16.9
redo log space requests 760 0.1 0.0
redo log space wait time 1,255 0.1 0.0
redo ordering marks 21 0.0 0.0
redo size 4,575,228,028 317,746.2 4,498.6
redo synch time 73,190 5.1 0.1
redo synch writes 333,440 23.2 0.3
redo wastage 240,517,096 16,703.7 236.5
redo write time 136,628 9.5 0.1
redo writer latching time 56 0.0 0.0
redo writes 865,653 60.1 0.9
rollback changes - undo records a 60,510 4.2 0.1
rows fetched via callback 3,948,006 274.2 3.9
session connect time 0 0.0 0.0
Statistic Total per Second per Trans
session logical reads 160,559,938 11,150.8 157.9
session pga memory 223,020,424 15,488.6 219.3
session pga memory max 841,058,240 58,410.9 827.0
session uga memory 682,912,005,944 47,427,738.5 671,472.1
session uga memory max 505,627,192 35,115.4 497.2
shared hash latch upgrades - no w 1,661,152 115.4 1.6
shared hash latch upgrades - wait 101 0.0 0.0
sorts (disk) 2 0.0 0.0
sorts (memory) 1,537,403 106.8 1.5
sorts (rows) 6,669,072 463.2 6.6
summed dirty queue length 71,613 5.0 0.1
switch current to new buffer 80,971 5.6 0.1
table fetch by rowid 79,047,167 5,489.8 77.7
table fetch continued row 5,013,545 348.2 4.9
table scan blocks gotten 10,328,271 717.3 10.2
table scan rows gotten 381,848,913 26,519.1 375.5
table scans (long tables) 82 0.0 0.0
table scans (short tables) 1,117,114 77.6 1.1
transaction rollbacks 32,437 2.3 0.0
transaction tables consistent rea 39 0.0 0.0
transaction tables consistent rea 82,904 5.8 0.1
user calls 1,186,828 82.4 1.2
user commits 1,017,037 70.6 1.0
user rollbacks 0 0.0 0.0
workarea executions - onepass 7 0.0 0.0
workarea executions - optimal 2,291,005 159.1 2.3
write clones created in backgroun 3 0.0 0.0
write clones created in foregroun 711 0.1 0.0
Class Waits Time (s) Time (ms)
data block 1,549,301 4,015 3
segment header 253 1 2
undo block 2,574 0 0
undo header 2,209 0 0
extent map 2 0 5
Eq Requests Succ Gets Failed Gets Waits Time (ms) Time (s)
TX 1,749,961 1,749,961 0 202 6.47 1
HW 20,789 20,789 0 223 .40 0
Pct Avg Wait Pct
Get Get Slps Time NoWait NoWait
Latch Requests Miss /Miss (s) Requests Miss
Consistent RBA 866,126 0.0 0.0 0 0
FIB s.o chain latch 594 0.0 0 0
FOB s.o list latch 2,891 0.0 0.0 0 0
SQL memory manager latch 4 0.0 0 4,793 0.0
SQL memory manager worka 3,266,221 0.0 0.0 0 0
active checkpoint queue 1,905,423 0.5 0.0 0 0
archive control 28 0.0 0 0
cache buffer handles 12,070 0.0 0 0
cache buffers chains 387,508,854 0.6 0.0 134 11,212,815 0.1
cache buffers lru chain 1,946,036 0.0 0.0 0 14,681,284 0.2
channel handle pool latc 668 0.0 0 0
channel operations paren 12,460 0.0 0.0 0 0
checkpoint queue latch 209,244,852 0.0 0.0 0 1,775,314 0.0
child cursor hash table 3,240 0.7 0.0 0 0
commit callback allocati 16 0.0 0 0
dictionary lookup 13 0.0 0 0
dml lock allocation 5,900,238 0.3 0.0 0 0
dummy allocation 894 0.2 0.0 0 0
enqueue hash chains 19,444,854 0.1 0.0 0 0
enqueues 9,380,299 0.7 0.0 0 0
event group latch 288 0.0 0 0
event range base latch 3 0.0 0 0
global tx hash mapping 4,988,645 0.0 0.0 0 0
hash table column usage 82 0.0 0 1,783 0.0
job workq parent latch 1 100.0 0.0 0 242 15.3
job_queue_processes para 287 0.0 0 0
ktm global data 265 0.0 0 0
lgwr LWN SCN 868,053 0.1 0.0 0 0
library cache 29,540,874 0.1 0.0 0 37 0.0
library cache load lock 102 0.0 0 0
library cache pin 24,145,848 0.0 0.0 0 0
library cache pin alloca 3,988,997 0.0 0.0 0 0
list of block allocation 363,684 0.0 0.0 0 0
loader state object free 912 0.0 0 0
longop free list parent 479 0.0 0 60 1.7
message pool operations 100 1.0 0.0 0 0
messages 8,036,523 0.3 0.0 0 0
mostly latch-free SCN 878,016 1.0 0.0 0 0
multiblock read objects 922,048 0.1 0.0 0 0
ncodef allocation latch 230 0.0 0 0
object stats modificatio 2,100 0.0 0 0
post/wait queue 709,603 0.0 0.0 0 334,338 0.0
process allocation 576 0.0 0 288 0.0
process group creation 576 0.2 0.0 0 0
redo allocation 18,881,467 0.7 0.0 0 0
redo copy 0 0 17,155,579 0.1
redo writing 4,513,716 0.2 0.0 0 0
resumable state object 48 0.0 0 0
row cache enqueue latch 3,556,148 0.1 0.0 0 0
row cache objects 6,671,783 0.1 0.0 0 0
Pct Avg Wait Pct
Get Get Slps Time NoWait NoWait
Latch Requests Miss /Miss (s) Requests Miss
sequence cache 1,533,482 0.0 0.0 0 0
session allocation 15,194,281 0.1 0.0 0 0
session idle bit 3,005,477 0.0 0.0 0 0
session switching 230 0.0 0 0
session timer 4,825 0.0 0 0
shared pool 2,114,153 0.0 0.0 0 0
sim partition latch 0 0 10,243 0.6
simulator hash latch 8,460,492 0.0 0.0 0 0
simulator lru latch 223,868 0.0 0.3 0 470,589 0.1
sort extent pool 1,823 0.5 0.0 0 0
temporary table state ob 16 0.0 0 0
transaction allocation 533,964 0.0 0 0
transaction branch alloc 1,259,723 0.1 0.0 0 0
undo global data 17,460,173 0.0 0.0 0 14,976 0.0
user lock 906 0.1 0.0 0 0
Get Spin &
Latch Name Requests Misses Sleeps Sleeps 1->4
cache buffers chains 387,508,854 2,447,832 12,701 2435135/1269
3/4/0/0
redo allocation 18,881,467 131,460 343 131118/341/1
/0/0
enqueues 9,380,299 62,436 122 62314/122/0/
0/0
library cache 29,540,874 38,344 80 38264/80/0/0
/0
messages 8,036,523 25,266 28 25238/28/0/0
/0
dml lock allocation 5,900,238 19,220 25 19195/25/0/0
/0
enqueue hash chains 19,444,854 10,510 27 10483/27/0/0
/0
active checkpoint queue la 1,905,423 9,896 36 9860/36/0/0/
0
library cache pin 24,145,848 8,451 17 8434/17/0/0/
0
mostly latch-free SCN 878,016 8,423 17 8406/17/0/0/
0
session allocation 15,194,281 8,290 33 8257/33/0/0/
0
redo writing 4,513,716 7,235 13 7222/13/0/0/
0
undo global data 17,460,173 4,113 8 4105/8/0/0/0
row cache objects 6,671,783 3,680 4 3676/4/0/0/0
row cache enqueue latch 3,556,148 2,015 1 2014/1/0/0/0
checkpoint queue latch 209,244,852 1,756 6 1750/6/0/0/0
transaction branch allocat 1,259,723 1,236 7 1229/7/0/0/0
shared pool 2,114,153 808 2 806/2/0/0/0
library cache pin allocati 3,988,997 649 1 648/1/0/0/0
cache buffers lru chain 1,946,036 588 13 575/13/0/0/0
multiblock read objects 922,048 469 8 461/8/0/0/0
sequence cache 1,533,482 333 1 332/1/0/0/0
session idle bit 3,005,477 97 1 96/1/0/0/0
Consistent RBA 866,126 55 1 54/1/0/0/0
simulator lru latch 223,868 33 9 24/9/0/0/0
post/wait queue 709,603 27 1 26/1/0/0/0
NoWait Waiter
Latch Name Where Misses Sleeps Sleeps
active checkpoint queue kcbbacq: scan active check 0 36 36
cache buffers chains kcbgtcr: kslbegin excl 0 10,706 10,084
cache buffers chains kcbrls: kslbegin 0 937 1,577
cache buffers chains kcbzwb 0 371 388
cache buffers chains kcbgtcr: fast path 0 223 174
cache buffers chains kcbgcur: kslbegin 0 86 114
cache buffers chains kcbget: pin buffer 0 57 47
cache buffers chains kcbzib: finish free bufs 0 54 27
cache buffers chains kcbchg: kslbegin: bufs not 0 52 89
cache buffers chains kcbnlc 0 46 37
cache buffers chains kcbzgb: scan from tail. no 0 42 0
cache buffers chains kcbzib: multi-block read: 0 25 0
cache buffers chains kcbget: exchange rls 0 12 3
cache buffers chains kcbchg: kslbegin: call CR 0 12 80
cache buffers chains kcbget: exchange 0 10 8
cache buffers chains kcbnew 0 9 0
cache buffers chains kcbcge 0 1 0
cache buffers chains kcbgtcr 0 1 0
cache buffers chains kcbbxsv 0 1 16
cache buffers chains kcbkzs 0 1 3
cache buffers chains kcbbic2 0 1 2
cache buffers chains kcbbic1 0 1 5
cache buffers lru chain kcbzgb: multiple sets nowa 10,344 10 0
cache buffers lru chain kcbbiop: lru scan 112 3 0
checkpoint queue latch kcbklbc: Link buffer into 0 6 0
dml lock allocation ktaiam 0 15 16
dml lock allocation ktaidm 0 10 9
enqueue hash chains ksqgtl3 0 17 11
enqueue hash chains ksqrcl 0 9 15
enqueue hash chains ksqcnl 0 1 1
enqueues ksqdel 0 60 50
enqueues ksqgel: create enqueue 0 60 56
enqueues ksqies 0 2 16
lgwr LWN SCN kcs023 0 9 0
library cache kglpnc: child 0 29 29
library cache kglupc: child 0 25 22
library cache kgllkdl: child: cleanup 0 11 2
library cache kglpndl: child: before pro 0 5 4
library cache kglhdgn: child: 0 3 13
library cache kglhdgc: child: 0 2 1
library cache kglpndl: child: after proc 0 2 0
library cache kgldte: child 0 0 1 2
library cache kglpin: child: heap proces 0 1 0
library cache kglobpn: child: 0 1 5
library cache pin kglpndl 0 6 1
library cache pin kglpnc: child 0 6 8
library cache pin kglupc 0 5 4
library cache pin alloca kglpnal 0 1 1
messages ksarcv 0 12 5
messages ksarcv: after wait 0 8 19
messages ksaamb: after wakeup 0 8 4
mostly latch-free SCN kcslcu3 0 8 17
mostly latch-free SCN kcsnew_scn_rba 0 1 0
Latch Name Where Misses Sleeps Sleeps
multiblock read objects kcbzib: mbr get 0 4 4
multiblock read objects kcbzib: normal mbr free 0 4 4
post/wait queue ksliwat:add:nowait 0 1 0
redo allocation kcrfwr 0 322 248
redo allocation kcrfwi: more space 0 14 88
redo allocation kcrfwi: before write 0 7 7
redo writing kcrfwcr 0 9 12
redo writing kcrfwint: rba scn pair 0 2 0
redo writing kcrfwint: after write 0 2 6
row cache enqueue latch kqreqa 0 1 1
row cache objects kqrpre: find obj 0 3 1
row cache objects kqrpfl: not dirty 0 1 1
sequence cache kdnss 0 1 1
session allocation ksuprc 0 14 5
session allocation ksudlc 0 10 7
session allocation ksucri 0 6 14
session allocation ksuxds: not user session 0 3 7
session idle bit ksupuc: clear busy 0 1 0
shared pool kghalo 0 1 0
shared pool kghupr1 0 1 2
simulator lru latch kcbs_simulate: simulate se 0 8 9
simulator lru latch kcbs_lookup_setid 0 1 0
transaction branch alloc ktcbba 0 4 2
transaction branch alloc ktcbod 0 2 3
transaction branch alloc ksupuc 0 1 2
undo global data ktudba: KSLBEGIN 0 8 7
Top 5 Logical Reads per Segment for DB: XXXXX Instance: XXXXX Snaps: 35980
-> End Segment Logical Reads Threshold: 10000
Subobject Obj. Logical
Owner Tablespace Object Name Name Type Reads %Total
xxxxxxxx XXXXXDATA TAB1TABLE TABLE 39,838,592 37.65
Top 5 Physical Reads per Segment for DB: XXXXX Instance: XXXXX Snaps: 3598
-> End Segment Physical Reads Threshold: 1000
Subobject Obj. Physical
Owner Tablespace Object Name Name Type Reads %Total
xxxxxxxx XXXXXDATA TAB1TABLE TABLE 3,568,038 58.64
Top 5 Buf. Busy Waits per Segment for DB: XXXXX Instance: XXXXX Snaps: 359
-> End Segment Buffer Busy Waits Threshold: 100
Buffer
Subobject Obj. Busy
Owner Tablespace Object Name Name Type Waits %Total
xxxxxxxx XXXXXDATA TAB1TABLE 1,421,043 91.65
xxxxxxxx XXXXXDATA IDX_SOMEIDX INDEX 62,638 4.04
xxxxxxxx XXXXXTABLE TABLE 26,914 1.74
----------So, for me It looks like :
TAB1TABLE is buffer busy deliver but there are no inserts reported for that table,
I've checked that TAB1TABLE tablespace is NO ASSM and extent management is local with uniform size 1M .
So this is not obvious free list problem . Kind of strange for me .
Any ideas greatly appreciated :).
Regards.
Greguser10388717 wrote:
Hi,
I've got statspack report from 9.2.0.8 DB, cpu_count = 12 , there is 'buffer busy waits' in top 5 .
Is there a problem ?
DB Name DB Id Instance Inst Num Release Cluster Host
XXXX 138180125 XXXX 1 9.2.0.8.0 NO X1
Snap Id Snap Time Sessions Curs/Sess Comment
Begin Snap: 35980 14-Jul-10 01:00:02 17 8.8
End Snap: 35984 14-Jul-10 05:00:01 17 8.8
Elapsed: 239.98 (mins)
----------So, for me It looks like :
TAB1TABLE is buffer busy deliver but there are no inserts reported for that table,
I've checked that TAB1TABLE tablespace is NO ASSM and extent management is local with uniform size 1M .
So this is not obvious free list problem . Kind of strange for me .
Any ideas greatly appreciated :).We can't tell if you have a problem - only you (or your users) can know.
But you've shown us a statspack snapshot covering 4 hours and in that time you've reported about 30 hours of database time (sum foreground "in-database" waits and CPU), with a fairly small number of sessions which (allowing for background sessions) means most of your foreground sessions seem to be working pretty much non-stop for the entire period. I could take a guess and say that you would like some of the work that they're doing completed sooner.
The largest fraction of your time goes into waiting for messages from db link, with an average time of 55ms - maybe you have a network problem, maybe you have a query that has a bad choice of execution path that is doing lots of unnecessary trips to the remote db, maybe the queries that get to the remote db could be made much more efficient. (Look for 'sql ordered by executions' in a statspack from the remote db for clues).
pl/sql lock timer is the next big chunk of time - but this is deliberately coded waits in pl/sql (dbms_lock.sleep) maybe that's supposed to be happening, but you could check the logic to see if some "slow" processes are actually coded to sleep much longer than necessary.
Your db file sequential reads (single block reads) are, on average taking 5.5 ms - which is reasonable, so you have to ask if the number (and we know which table a lot of them are hitting) is reasonable. This brings us to your buffer busy waits: these can be caused by updates and deletes as well as inserts, but in 9i they are also caused by "read by other session" - so the buffer busy wait may simple be one session waiting for another session to complete a db file sequential read.
I'd look at your "SQL ordered by Reads" to see if you have some inefficient execution plans (or poorly defined indexes) that result in large amounts of the critical table being constantly re-read. It's possible that you can eliminate redundant visits to this table and reduce your I/O, BBW, and CPU in one shot.
Regards
Jonathan Lewis -
Can you please provide me the suggestion on how to reduce the number of buffer busy waits for the below query?
Please find the query where the buffer busy waits is taking 11091 and 13160 seconds.
INSERT INTO RPM_CLEARANCE (CLEARANCE_ID, CLEARANCE_DISPLAY_ID, STATE,
REASON_CODE, CLEARANCE_RESET_ID, RESET_IND, ITEM, ZONE_ID, LOCATION,
ZONE_NODE_TYPE, EFFECTIVE_DATE, OUT_OF_STOCK_DATE, RESET_DATE, CHANGE_TYPE,
CHANGE_AMOUNT, CHANGE_PERCENT, CHANGE_CURRENCY, VENDOR_FUNDED_IND,
CREATE_DATE, CREATE_ID, APPROVAL_DATE, APPROVAL_ID, TSL_EVENT_REF,
TSL_MARKDOWN_REF, TSL_EVENT_PHASE, TSL_COVER_GROUP, TSL_END_DATE,
TSL_EVENT_POS_IND, TSL_EVENT_SEL_IND, TSL_HOPOS_TEMPLATE_ID )
VALUES
(:B23 , 'reset:'||:B22 , :B21 , :B20 , NULL, '1', :B19 , :B18 , :B17 , :B16 ,
:B15 , :B15 - 1, NULL, :B14 , :B13 , :B12 , :B11 , '0', :B10 , :B9 , :B10 ,
:B9 , :B8 , :B7 , :B6 , :B5 , :B4 , :B3 , :B2 , :B1 )
call count cpu elapsed disk query current rows
Parse 1849 0.06 0.05 0 0 0 0
Execute 1895091 2539.06 2606.23 32 119694 31084693 1895091
Fetch 0 0.00 0.00 0 0 0 0
total 1896940 2539.12 2606.28 32 119694 31084693 1895091
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 202 (recursive depth: 1)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
db file sequential read 32 0.01 0.22
buffer busy waits 11091 0.02 0.29
latch: cache buffers chains 30 0.00 0.00
enq: TX - index contention 563 0.01 0.11
log file switch completion 15 0.06 0.42
latch: In memory undo latch 7 0.00 0.00
buffer deadlock 88 0.00 0.00
cursor: pin S 59 0.00 0.00
cursor: pin S wait on X 1 0.00 0.00
INSERT INTO RPM_CLEARANCE (CLEARANCE_ID, CLEARANCE_DISPLAY_ID, STATE,
REASON_CODE, CLEARANCE_RESET_ID, RESET_IND, ITEM, ZONE_ID, LOCATION,
ZONE_NODE_TYPE, EFFECTIVE_DATE, OUT_OF_STOCK_DATE, RESET_DATE, CHANGE_TYPE,
CHANGE_AMOUNT, CHANGE_PERCENT, CHANGE_CURRENCY, VENDOR_FUNDED_IND,
CREATE_DATE, CREATE_ID, APPROVAL_DATE, APPROVAL_ID, TSL_EVENT_REF,
TSL_MARKDOWN_REF, TSL_EVENT_PHASE, TSL_COVER_GROUP, TSL_END_DATE,
TSL_EVENT_POS_IND, TSL_EVENT_SEL_IND, TSL_HOPOS_TEMPLATE_ID )
VALUES
(:B23 , 'reset:'||:B22 , :B21 , :B20 , NULL, '1', :B19 , :B18 , :B17 , :B16 ,
:B15 , :B15 - 1, NULL, :B14 , :B13 , :B12 , :B11 , '0', :B10 , :B9 , :B10 ,
:B9 , :B8 , :B7 , :B6 , :B5 , :B4 , :B3 , :B2 , :B1 )
call count cpu elapsed disk query current rows
Parse 575 0.02 0.01 0 0 0 0
Execute 1066687 1460.30 1478.77 0 121065 17556349 1066687
Fetch 0 0.00 0.00 0 0 0 0
total 1067262 1460.32 1478.79 0 121065 17556349 1066687
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 202 (recursive depth: 1)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
latch: cache buffers chains 28 0.01 0.01
buffer busy waits 13160 0.07 0.46
enq: TX - index contention 522 0.00 0.09
buffer deadlock 108 0.00 0.00
latch: In memory undo latch 17 0.00 0.00
cursor: pin S 8 0.00 0.00
log file switch completion 2 0.05 0.07
cursor: pin S wait on X 1 0.00 0.00
********************************************************************************For reducing buffer busy waits you need to increase DB_CACHE_SIZE parameter value.
Try the query below
14:40:23 SQL> select name,size_for_estimate,size_factor,estd_physical_reads,buffers_for_estimate fro
m v$db_cache_advice order by 4;
NAME SIZE_FOR_ESTIMATE SIZE_FACTOR ESTD_PHYSICAL_READS BUFFERS_FOR_ESTIMATE
DEFAULT 960 1.875 252983 119760
DEFAULT 912 1.7813 268597 113772
DEFAULT 864 1.6875 269415 107784
DEFAULT 816 1.5938 269673 101796
DEFAULT 768 1.5 270449 95808
DEFAULT 720 1.4063 270923 89820
DEFAULT 672 1.3125 272107 83832
DEFAULT 624 1.2188 276651 77844
DEFAULT 576 1.125 282272 71856
DEFAULT 528 1.0313 308869 65868
DEFAULT 512 1 334346 63872
DEFAULT 480 .9375 411617 59880
DEFAULT 432 .8438 467955 53892
DEFAULT 384 .75 520223 47904
DEFAULT 336 .6563 575829 41916
DEFAULT 288 .5625 628226 35928
DEFAULT 240 .4688 670286 29940
DEFAULT 192 .375 725289 23952
DEFAULT 144 .2813 784512 17964
DEFAULT 96 .1875 921481 11976
DEFAULT 48 .0938 1948144 5988
21 rows selected.You will get a result like above. SIZE_FOR_ESTIMATE column shows values in MB.
Then from the result, choose a size for the buffer cache in which there is minimal physical reads but according to the avaliability of your physical memory and set it. -
Buffer Busy Waits on Primary Keys - RKI
11.2.03 - HPUX
Hi All.
We're seeing significant Buffer Busy Waits (around 15% of non idle waits during bad times) and most of the contention is on the following;
SYS.SEQ$, and two primary keys..
The primary key one seems easier to fix in the first instance, with most of the expert thinking seeming to be either Reverse Key Indexes, or hash partitions for index. Thinking this through, wouldn't moving from normal key order to reverse key order cause a lot more I/O - if the assumption is that the rows being queried are likely to be the newer rows being inserted?? If we scatter them evenly among the index segment - won't that have a deleterious effect on I/O for that segment? In effect we're swapping Buffer Busy Waits for much worse (?) I/O?>
We're seeing significant Buffer Busy Waits (around 15% of non idle waits during bad times) and most of the contention is on the following;
SYS.SEQ$, and two primary keys..
The primary key one seems easier to fix in the first instance, with most of the expert thinking seeming to be either Reverse Key Indexes, or hash partitions for index. Thinking this through, wouldn't moving from normal key order to reverse key order cause a lot more I/O - if the assumption is that the rows being queried are likely to be the newer rows being inserted?? If we scatter them evenly among the index segment - won't that have a deleterious effect on I/O for that segment? In effect we're swapping Buffer Busy Waits for much worse (?) I/O?
>
If you have heavy INSERTs, especially in RAC, you need to solve your current problem. But you need to make sure you know what that problem is.
You have likely identified it but you should take a quick look at your sequence and the cache value being used. Contention on SEQ$ could mean that you are using NOCACHE or a low value for CACHE.
If your primary key accesses typically access just one row it won't really matter if those rows are 'scattered'. It sounds like you are thinking that queries of 'newer' rows will make it likely that those queries will need the same blocks because the rows will be sharing a block.
But why would users be accessing data using a non-meaningful sequence number? I wouldn't expect users to even know what the primary key value was to be able to query it. I would expect them to be querying based on a business value, company_code or date.
Can you explain why you are worried about that?
You might be interested in this two part article about reverse key indexes by Richard Foote
http://richardfoote.wordpress.com/2008/01/14/introduction-to-reverse-key-indexes-part-i/
http://richardfoote.wordpress.com/2008/01/16/introduction-to-reverse-key-indexes-part-ii-another-myth-bites-the-dust/
>
Reverse Key Indexes are designed to resolve a specific issue, that being index block contention. Many indexes in busy database environments with lots of concurrent inserts (and in some scenarios updates and deletes as well) can suffer from index block contention (as highlighted by high levels of “buffer busy waits” and “read by other session” wait events for the index segments). Monotonically increasing indexes, such as Primary Keys generated by a sequence, are especially prone to contention as all inserts need to access the maximum “right-most” leaf block. This is of particular concern in RAC environments, where this “hot” index block needs to be accessed by all the instances and is being bounced around the various SGAs causing expensive block transfers between instances.
A solution is make the index a Reverse Key Index. -
Buffer busy waits yet another issue.
Hi,
Here is the scenario we are facing.
The application is trying to insert the data into one of the partition and the table on which this buffer busy waits is occuring is on an tablespace with ASSM and extent management auto.
total number of inserts done only 137
The application issues only the insert and update statements, so here the waits are dominant only for the insert statements,
This particular table is range partitioned and the PCTFREE is set to 10, and the size of the partitions ranges from 138-150Mb.
checked that the waits are caused due to the data blocks.
After checking the P2 parameter found out that the insert statements are waiting on only one particular block.
Average row length is only 177bytes, and the database block size is 8Kb, the table is not accessed very frequently, ruling all the other factor out except increasing the PCTFREE.
when all the blocks of the current table are filled, now when we issue an insert statement a new extent is allocated to the table and is brought into the memory for inserting and... now my question is as this is the only block that is present in the memory does all the inserts happen only on this block or whether the oracle is intellegent enough to bring all the blocks in the new extent to be brought to the memory and spreads the inserts to all teh blocks in the newly allocated extent. (i believe this assumption is wrong as this can lead to much memory wastage)..
Dont understand why simple insert statements that too only about 137 can cause serious busy busy waits...
Please provide your suggestions.
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE 11.2.0.2.0 Production
TNS for IBM/AIX RISC System/6000: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production900486 wrote:
Dont understand why simple insert statements that too only about 137 can cause serious busy busy waits...
There are a few possibilities.
Nice hints at http://docs.oracle.com/cd/B19306_01/em.102/b25986/oracle_database.htm and I like Jonathan's (older) note at http://www.jlcomp.demon.co.uk/bbw.html (recreated from Howard's site). Sone possible resolutions at http://www.confio.com/English/Tips/Buffer_Busy_Waits.php
An excellent discussion found in http://www.amazon.com/Oracle-Wait-Interface-Performance-Diagnostics/dp/007222729X as well.
If you have licensed Diagnostics Pack, perhaps you could shre your AWR/ASH reports? -
Buffer Busy Waits in a Read-Mostly Database?
11gR2 Standard Edition on Linux x86_64.
The database consists of two large tables (12GB+), one column of each of which has an Oracle Text index on it. Once a month, the two tables are refreshed from elsewhere, the Text indexes are updated, and then they sit there for the rest of the month, effectively read-only as users perform full text searches. The instance runs in 20GB of RAM, of which 16GB is given over to the (8K, default) buffer cache, 1GB SGA, 2GB PGA.
The principle recurring wait event on this database is buffer busy waits, for data blocks (i.e., not undo segment headers) -and the data blocks are those of the two tables (which have default freelists, freelist groups and initrans and maxtrans).
I get that during the monthly refresh, when there's loads of inserts happening, there could be lots of buffer busy waits. Since that refresh happens at weekends out-of-hours, waits during that time are not of any great concern.
My question is why there would be any such waits during the database's 'read-only' period, in between refreshes. I can positively guarantee that no DML is taking place then, yet the buffer busy waits still occur, from time to time.
On a possibly related note, why would I see lots of "consistent reads" during the 'read-only' period? The data isn't changing at all, so why would the database be busy doing consistent reads when current reads (I would have thought) would be good enough to get the data in the state it's actually at?Catfive Lander wrote:
11gR2 Standard Edition on Linux x86_64.
The database consists of two large tables (12GB+), one column of each of which has an Oracle Text index on it. Once a month, the two tables are refreshed from elsewhere, the Text indexes are updated, and then they sit there for the rest of the month, effectively read-only as users perform full text searches. The instance runs in 20GB of RAM, of which 16GB is given over to the (8K, default) buffer cache, 1GB SGA, 2GB PGA.
The principle recurring wait event on this database is buffer busy waits, for data blocks (i.e., not undo segment headers) -and the data blocks are those of the two tables (which have default freelists, freelist groups and initrans and maxtrans).
I get that during the monthly refresh, when there's loads of inserts happening, there could be lots of buffer busy waits. Since that refresh happens at weekends out-of-hours, waits during that time are not of any great concern.
My question is why there would be any such waits during the database's 'read-only' period, in between refreshes. I can positively guarantee that no DML is taking place then, yet the buffer busy waits still occur, from time to time.
On a possibly related note, why would I see lots of "consistent reads" during the 'read-only' period? The data isn't changing at all, so why would the database be busy doing consistent reads when current reads (I would have thought) would be good enough to get the data in the state it's actually at?Catfive,
Are you running 11.2.0.1 or 11.2.0.2? If you are running 11.2.0.1 there are at least two bugs fixed by 11.2.0.2 to correct problems that lead to buffer busy waits. You mentioned that this is a "mostly" read only database where you are experiencing these waits - does that mean that there might be some inserts, updates, and deletes (possibly auditing related?)? One of the bug reports found on Metalink (MOS) is this one:
Doc ID 9341448.8, Bug 9341448 - "Buffer block contention on full block which keeps being tried for space"
How did you determine that the buffer busy waits were related to these two tables? Did you check V$SEGMENT_STATISTICS, monitor the session level wait events, create a 10046 trace at level 8 or 12, or use some other method? Are these tables typically read using parallel execution? Is there any chance that the application is performing SELECT ... FOR UPDATE?
Have you checked V$SESSION_EVENT to see which sessions waited on buffer busy waits? How severe are the buffer busy waits - 10 seconds in a 24 hour period, 1 minute in a 20 minute time period? Are you backing up this database using RMAN and comparing the change in the buffer busy waits before and after RMAN completes its backup?
I wonder if using SGA_TARGET could lead to buffer busy waits during an automatic buffer cache resize operation?
Regarding seeing "consistent reads" during the read only period, that should be expected when blocks are read from the buffer cache. Jonathan Lewis explained it well in at least one of the threads that he contributed to on OTN, but I cannot find that thread at the moment. Essentially (in as few words as possible), you will see current mode block accesses when the data blocks are being changed and consistent reads (consistent gets) when the blocks are being read. This thread includes comments that suggest what to check to determine if undo had to be applied to perform the consistent gets:
Index consists 1.5mln blocks, but full scan gets 11mln blocks
Edit:
I found the thread with Jonathan's comment:
high consistent read during parse call | tkprof output
"If you're not doing a current read then the only alternative is to do a consistent read.
Typically you do current reads because you want to change a block"
Charles Hooper
Co-author of "Expert Oracle Practices: Oracle Database Administration from the Oak Table"
http://hoopercharles.wordpress.com/
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc.
Edited by: Charles Hooper on Jan 5, 2011 8:45 AM
Added link to second OTN thread -
High Buffer Busy Wait due to Concurrent INSERTS
Hi All,
One of my OLTP database is running on 11.1.0.7 (11.1.0.7.0 - 64bit Production) with RHEL 5.4.
On frequent basis, i am observing 'BUFFER BUSY WAITS' and last time i tried to capture some dictionary information to dig the waits.
1. Session Watis :
Oracle Sec Hash
Sid,Serial User OS User Svr-Pgm Wait Event State-Seq Wt Module Cmnd Value P1 P2 P3
633,40830 OLTP_USE fateadm 21646-orac buffer busy wai Wtng-9999 1 ORDERS ISRT 3932487748 384 1863905 1
647, 1761 OLTP_USE fateadm 22715-orac buffer busy wai Wtng-3837 0 ORDERS ISRT 3932487748 384 1863905 1
872, 5001 OLTP_USE fateadm 21836-orac buffer busy wai Wtng-9999 1 ORDERS ISRT 3932487748 384 1863905 1
702, 1353 OLTP_USE fateadm 21984-orac buffer busy wai Wtng-9999 1 ORDERS ISRT 3932487748 384 1863905 1
337,10307 OLTP_USE fateadm 21173-orac buffer busy wai Wtng-9999 1 ORDERS ISRT 3932487748 384 1863905 1
751,43016 OLTP_USE fateadm 21619-orac buffer busy wai Wtng-9999 1 ORDERS ISRT 3932487748 384 1863905 1
820,17959 OLTP_USE fateadm 21648-orac buffer busy wai Wtng-9999 0 ORDERS ISRT 3932487748 384 1863905 1
287,63359 OLTP_USE fateadm 27053-orac buffer busy wai Wtng-9999 0 ORDERS ISRT 3932487748 384 1863905 1
629, 1653 OLTP_USE fateadm 22468-orac buffer busy wai Wtng-9999 1 ORDERS ISRT 3932487748 384 1863905 1
788,14160 OLTP_USE fateadm 22421-orac buffer busy wai Wtng-9999 0 ORDERS ISRT 3932487748 384 1863905 1
615, 4580 OLTP_USE fateadm 21185-orac buffer busy wai Wtng-9999 0 ORDERS ISRT 3932487748 384 1863905 1
525,46068 OLTP_USE fateadm 27043-orac buffer busy wai Wtng-9034 1 ORDERS ISRT 3932487748 384 1863905 1
919,23243 OLTP_USE fateadm 21428-orac buffer busy wai Wtng-6340 1 ORDERS ISRT 3932487748 384 1863906 1
610,34557 OLTP_USE fateadm 21679-orac buffer busy wai Wtng-6422 1 ORDERS ISRT 3932487748 384 1863906 1
803, 1583 OLTP_USE fateadm 21580-orac buffer busy wai Wtng-6656 1 ORDERS ISRT 3932487748 384 1863906 1
781, 1523 OLTP_USE fateadm 21781-orac buffer busy wai Wtng-9999 0 ORDERS ISRT 3932487748 384 1863906 1
369,11005 OLTP_USE fateadm 21718-orac buffer busy wai Wtng-9999 0 ORDERS ISRT 3932487748 384 1863906 1
823,35800 OLTP_USE fateadm 21148-orac buffer busy wai Wtng-9999 1 ORDERS ISRT 3932487748 384 1863906 1
817, 1537 OLTP_USE fateadm 22505-orac buffer busy wai Wtng-9999 1 ORDERS ISRT 3932487748 384 1863906 1
579,54959 OLTP_USE fateadm 22517-orac buffer busy wai Wtng-9999 0 ORDERS ISRT 3932487748 384 1863906 1
591,33597 OLTP_USE fateadm 27027-orac buffer busy wai Wtng-9999 1 ORDERS ISRT 3932487748 384 1863906 1
481, 3031 OLTP_USE fateadm 21191-orac buffer busy wai Wtng-3502 1 ORDERS ISRT 3932487748 384 1863906 1
473,24985 OLTP_USE fateadm 22629-orac buffer busy wai Wtng-9999 0 ORDERS ISRT 3932487748 384 1863906 1
868, 3984 OLTP_USE fateadm 27191-orac buffer busy wai Wtng-9999 0 ORDERS ISRT 3932487748 384 1863906 1
select owner,segment_name,segment_type from dba_extents where file_id = 384 and 1863905 between block_id and block_id + blocks -1;
OWNER SEGMENT_NAME SEGMENT_TYPE
ORDER ORDER_DETAILS TABLE
select TABLE_NAME,PARTITIONED,ini_trans ,degree,compression,FREELISTS from dba_TABLES WHERE TABLE_NAME='ORDER_DETAILS';
TABLE_NAME PAR INI_TRANS DEGREE COMPRESS FREELISTS
ORDER_DETAILS NO 1 1 ENABLED 1
Tablespace is not ASSM managed !
select
object_name,
statistic_name,
value
from
V$SEGMENT_STATISTICS
where
object_name = 'ORDER_DETAILS';
OBJECT_NAME STATISTIC_NAME VALUE
ORDER_DETAILS logical reads 487741104
ORDER_DETAILS buffer busy waits 4715174
ORDER_DETAILS db block changes 200858896
ORDER_DETAILS physical reads 143642724
ORDER_DETAILS physical writes 20581330
ORDER_DETAILS physical reads direct 55239903
ORDER_DETAILS physical writes direct 19500551
ORDER_DETAILS space allocated 1.6603E+11
ORDER_DETAILS segment scans 9727
ORDER_DETAILS table is ~ 153 GB non-partitioned table.
It seems its not a READ BY OTHER SESSIONS wait but BUFFER BUSY due to write-wirte contention inside same block. I have never observed Cache Buffer Chain/ ITL-Wait/ High wait time on dbfile sequential/scattered reads.Table contains one PK (composite index on 3 columns) which seems to be highly fragmented.This non partitioned global Index has 3182037735 rows and blevel is 4.
BHAVIK_DBA.FATE1NA>select index_name,status,num_rows,blevel,pct_free,ini_trans,clustering_factor from dba_indexes where index_name='IDX_ORDERS';
INDEX_NAME STATUS NUM_ROWS BLEVEL PCT_FREE INI_TRANS CLUSTERING_FACTOR
IDX_ORDERS VALID 3182037735 4 2 2 2529462377
1 row selected.
One of the index column value is being populated by sequence. (Monotonically increasing value)
SEGMENT_NAME MB
IDX_ORDERS 170590.438
Index size is greater than table size !Tuning goal here is to reduce buffer busy waits and thus commit latencies.
I think, i need to increase FREELISTS and PCT_FREE to address this issue, but not much confident whether it is going to solve the issue or not?
Can i ask for any help here ?Hi Johnathan;
Many thanks for your detailed write-up. I was expecting you !
Your post here gave lot of information and wisdom that made me think last couple of hrs that is the reason for the delay in reply.
I did visited your index explosion posts couple of times and that scenario only gave me insight that concurrent DML (INSERT) is cause of index fragmentation in my case.
Let me also pick the opportunity to ask you to shed more light on some of the information you have highlighted.
if you can work out the number of concurrent inserts that are really likely to happen at any one instant then a value of freelists that in the range of
concurrency/4 to concurrency/2 is probably appropriate.May i ask you how did you derive this formula ? I dont want to miss learning opportunity here !
Note - with multiple freelists, you may find that you now get buffer busy waits on the segment header block.I did not quite get this point ? Can you shed more light please? What piece in segment header block is going to result contention(BBW on SEGMENT HEADER) on all concurrent inserts ?
The solution to this is to increase the number of freelist groups (making sure that
freelists and freelist groups have no common factors).My prod db NON-RAC environment. Can i use FREELIST GROUPS here ? My little knowledge did not get, What "common factors" you are referring here ?
The reads could be related to leaf block splits, but there are several possible scenarios that could lead to that pattern of activity - so the next step is to find out which blocks are being
read. Capture a sample of the waits, then query dba_extents for the extent_id, file_id, and block_id (don't run that awful query with the "block_id + blocks" predicate) and cross-check the
list of blocks to see if they are typically the first couple of blocks of an extent or randomly scattered throughout extents. If the former the problem is probably related to ASSM, if the
latter it may be related to failed probes on index leaf block reuse (i.e. after large scale deletes).I have 10046 trace file with me (giving you some sample below) that can give some information. However, since the issue was critical, i killed the insert process and rebuilt both the indexes. Since, index is rebuilt, i am not able to find any information in dba_extents.
select SEGMENT_NAME,SEGMENT_TYPE,EXTENT_ID from dba_extents where file_id=42 and block_id=1109331;
no rows selected
select SEGMENT_NAME,SEGMENT_TYPE,EXTENT_ID from dba_extents where file_id=42 and block_id=1109395 ;
no rows selected
select SEGMENT_NAME,SEGMENT_TYPE,EXTENT_ID from dba_extents where file_id=42 and block_id=1109459;
no rows selected
select SEGMENT_NAME,SEGMENT_TYPE,EXTENT_ID from dba_extents where file_id=10 and block_id=1107475;
no rows selected
select SEGMENT_NAME,SEGMENT_TYPE,EXTENT_ID from dba_extents where file_id=10 and block_id=1107539;
no rows selected
select object_name,object_Type from dba_objects where object_id=17599;
no rows selected
WAIT #4: nam='db file sequential read' ela= 49 file#=42 block#=1109331 blocks=1 obj#=17599 tim=1245687162307379
WAIT #4: nam='db file sequential read' ela= 59 file#=42 block#=1109395 blocks=1 obj#=17599 tim=1245687162307462
WAIT #4: nam='db file sequential read' ela= 51 file#=42 block#=1109459 blocks=1 obj#=17599 tim=1245687162307538
WAIT #4: nam='db file sequential read' ela= 49 file#=10 block#=1107475 blocks=1 obj#=17599 tim=1245687162307612
WAIT #4: nam='db file sequential read' ela= 49 file#=10 block#=1107539 blocks=1 obj#=17599 tim=1245687162307684
WAIT #4: nam='db file sequential read' ela= 198 file#=10 block#=1107603 blocks=1 obj#=17599 tim=1245687162307905
WAIT #4: nam='db file sequential read' ela= 88 file#=10 block#=1107667 blocks=1 obj#=17599 tim=1245687162308016
WAIT #4: nam='db file sequential read' ela= 51 file#=10 block#=1107731 blocks=1 obj#=17599 tim=1245687162308092
WAIT #4: nam='db file sequential read' ela= 49 file#=10 block#=1107795 blocks=1 obj#=17599 tim=1245687162308166
WAIT #4: nam='db file sequential read' ela= 49 file#=10 block#=1107859 blocks=1 obj#=17599 tim=1245687162308240
WAIT #4: nam='db file sequential read' ela= 52 file#=10 block#=1107923 blocks=1 obj#=17599 tim=1245687162308314
WAIT #4: nam='db file sequential read' ela= 57 file#=42 block#=1109012 blocks=1 obj#=17599 tim=1245687162308395
WAIT #4: nam='db file sequential read' ela= 52 file#=42 block#=1109076 blocks=1 obj#=17599 tim=1245687162308470
WAIT #4: nam='db file sequential read' ela= 98 file#=42 block#=1109140 blocks=1 obj#=17599 tim=1245687162308594
WAIT #4: nam='db file sequential read' ela= 67 file#=42 block#=1109204 blocks=1 obj#=17599 tim=1245687162308686
WAIT #4: nam='db file sequential read' ela= 53 file#=42 block#=1109268 blocks=1 obj#=17599 tim=1245687162308762
WAIT #4: nam='db file sequential read' ela= 54 file#=42 block#=1109332 blocks=1 obj#=17599 tim=1245687162308841
WAIT #4: nam='db file sequential read' ela= 55 file#=42 block#=1109396 blocks=1 obj#=17599 tim=1245687162308920
WAIT #4: nam='db file sequential read' ela= 54 file#=42 block#=1109460 blocks=1 obj#=17599 tim=1245687162308999
WAIT #4: nam='db file sequential read' ela= 52 file#=10 block#=1107476 blocks=1 obj#=17599 tim=1245687162309074
WAIT #4: nam='db file sequential read' ela= 89 file#=10 block#=1107540 blocks=1 obj#=17599 tim=1245687162309187
WAIT #4: nam='db file sequential read' ela= 407 file#=10 block#=1107604 blocks=1 obj#=17599 tim=1245687162309618TKPROF for above trace
INSERT into
order_rev
(aggregated_revenue_id,
legal_entity_id,
gl_product_group,
revenue_category,
warehouse_id,
tax_region,
gl_product_subgroup,
total_shipments,
total_units_shipped,
aggregated_revenue_amount,
aggregated_tax_amount,
base_currency_code,
exchange_rate,
accounting_date,
inventory_owner_type_id,
fin_commission_structure_id,
seller_of_record_vendor_id,
organizational_unit_id,
merchant_id,
last_updated_date,
revenue_owner_type_id,
sales_channel,
location)
VALUES
(order_rev.nextval,:p1,:p2,:p3,:p4,:p5,:p6,:p7,:p8,:p9,:p10,:p11,:p12,to_date(:p13, 'dd-MON-yyyy'),:p14,:p15,:p16,:p17,:p18,sysdate,:p19,:p20,:p21)
call count cpu elapsed disk query current rows
Parse 0 0.00 0.00 0 0 0 0
Execute 613 5.50 40.32 96672 247585 306916 613
Fetch 0 0.00 0.00 0 0 0 0
total 613 5.50 40.32 96672 247585 306916 613
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 446
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
db file sequential read 164224 0.04 62.33
SQL*Net message to client 613 0.00 0.00
SQL*Net message from client 613 0.03 0.90
latch: cache buffers chains 8 0.00 0.00
latch: object queue header operation 2 0.00 0.00Is there any other way to find out culprit amongst the two you have listed (ASSM / failed probes on index leaf block reuse ) ? -
Buffer busy wait, 1st level bmp
Hi All !
OS: Linux redhat 5
DB: 11gr2
Block size: 8K
In an application we use I can see high buffer busy waits over a various periods.
I collect some info during this event.
SQL_HASH_VALUE FILE# BLOCK# REASON
769132182 6 17512 8
3983195767 6 17512 8
769132182 6 17512 8
3240261994 6 17512 8
3240261994 6 17512 8
3240261994 6 17512 8
769132182 6 17512 8
... I have total 35 sessions
File6 / block 17512 =
TABLESPACE_NAME SEGMENT_TYPE OWNER SEGMENT_NAME
GBSLOB LOBSEGMENT GBSASP SYS_LOB0000017961C00006$$
The sql are both inserts and updates to the same large table, blobs are involved (insert/update)
blobs using securefile
AWR reports this for a short period
Buffer busy waits is the top wait event
Buffer Wait Statistics DB/Inst: GGBISP01/ggbisp01 Snaps: 20925-20926
-> ordered by wait time desc, waits desc
Class Waits Total Wait Time (s) Avg Time (ms)
1st level bmb 574,636 17,118 30
free list 20,538 70 3
undo header 41,150 7 0
data block 263 1 3
undo block 18 0 0
I'm trying to find more details about this wait event, I believe it is related to usage of ASSM.
Can anyone explain more when 1st level bmp is seen ?
Thank you !
Best regards
Magnus JohanssonMaJo wrote:
SQL_HASH_VALUE FILE# BLOCK# REASON
769132182 6 17512 8
3983195767 6 17512 8
769132182 6 17512 8
3240261994 6 17512 8
3240261994 6 17512 8
3240261994 6 17512 8
769132182 6 17512 8
... I have total 35 sessions
File6 / block 17512 =
TABLESPACE_NAME SEGMENT_TYPE OWNER SEGMENT_NAME
GBSLOB LOBSEGMENT GBSASP SYS_LOB0000017961C00006$$The sql are both inserts and updates to the same large table, blobs are involved (insert/update)
blobs using securefile
AWR reports this for a short period
Buffer busy waits is the top wait event
Buffer Wait Statistics DB/Inst: GGBISP01/ggbisp01 Snaps: 20925-20926
-> ordered by wait time desc, waits desc
Class Waits Total Wait Time (s) Avg Time (ms)
1st level bmb 574,636 17,118 30
free list 20,538 70 3
undo header 41,150 7 0
data block 263 1 3
undo block 18 0 0
-------------------------------------------------------------I'm trying to find more details about this wait event, I believe it is related to usage of ASSM.
Can anyone explain more when 1st level bmp is seen ?
Your AWR shows an interesting mix of ASSM and freelist group blocks - are you running ASSM ?
1st level bitmap blocks (bmb) are the blocks in a segment (usually the first one or two of each extent) that show the availability of free space in the other data blocks. Each bitmap block can identify up to 256 other blocks (the last time I checked), although you have to have a fairly large data segment before you reach this level of mapping.
If you have a high rate of concurrent inserts and updates on a LOB column then you may be running into code that frequently updates bitmap blocks to show that data blocks have changed from empty to full. It's also possible that you've run into one of the many bugs that appeared when you mixed ASSM with LOB segments - you haven't given the exact version of 11.2, but you might want to check the latest versions and any bug reports for patches to your version.
Regards
Jonathan Lewis -
HI,
I am facing a problem of gc buffer busy waits and log file switch completion on my live rac database of two nodes.
Thank you for your cooperation.
Regards,
Adnan Hamdus SalamAman.... wrote:
I am sorry sir. I gave that link for the gc buffer busy wait only and overlooked the log file switch part.
No need to apologise, or call me sir (the English and American use of the words have very different connotations). I was just adding an extra detail to go with a useful reference.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk
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If you never mark your questions as answered people will eventually decide that it's not worth trying to answer you because they will never know whether or not their answer has been of any use, or whether you even bothered to read it.
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High waits on scatter read and buffer busy wait ..
one of my system is undergoing some serious problem ~
i checked when some sql querying few large tables ( 30 millions rows ,partioned )
system waits became significant .. the ones stand out are scatter read and buffer busy wait ...
on the longop , you can see those sessions waitting to scan the large table ..
buffer get ratio dropped from 90% to like 30% ,average buffer hit ratio is like 55%
mu questions are
1.what's your view of throwing the problem away ?
add physical memory, then increase data buffer ?
it's getting scanned very often , but it's too large to pin it in the keep pool .
2. why buffer busy wait ?
i don't fully understand why this happened ?
becase what they are doing are just querying ,nobody is modifing any data ?
will increase freelist help this ??
thanks your talneted ideas
br/rickyHave these SQL statements been added recently, or have they been around for a long time. If the latter, then it seems likely that they've changed their execution plan to start doing tablescans (hence db file scattered read waits) or index fast full scans.
One of the causes of buffer busy waits is concurrent tablescans/index fast full scans - in 10g this particular cause has been split and reported as "read by other session".
Your first action should be to see if there is a more efficient execution plan for these queries. If the problem is due to a change in execution plan, common causes are: changes in statistics on the objects, failure to change statistics on the objects, changes in input value on the queries, changes in optimizer parameters, unlucky changes in data volumes.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk
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