Checkpoint vs. log file switch
Hi..
Does Oracle flush all dirty buffers at log file switch or just a part of dirty buffers?
Doc says Full checkpoint occurs only by commands (Shutdonw or checkpoint command). I guess the meaning of this is that log file switch doen's flush all dirty buffers..I want to get some more infomaton on this.
Thanks
Hi Jonathan,
Thank you for participating in the OTN topics.
At any full checkpoint (log switch or command) DBWR
is triggered to walk the checkpoint queue and write
all the blocks that are currently on it - i.e. all
the currently dirty blocks. Obviously this can take
some time, but the task has a known completion point
because of the queue structure.Once I've red interesting article published on Oracle Magazine RE two years ago.
Author states (and there is no reason to distrust him) that after log switch so called low priority normal checkpoint takes place in contrast to incremental checkpoint when DBWR will perform actual writes to disk. It is not necessarily for DBWR to start checkpoint writes at the log switch immediately.
I played a bit experimenting with log switch, global checkpoint etc making many DML at the same time to supply DBWR with dirty blocks but algorith used by Oracle is not clear at all.
I observed that ckpt_block_writes in the v$instance_recovery view is not increasing after log switch but instead it increments occasionally (by incremental checkpoint starting I suppose).
Can you please put some comments about this.
Your opinion is really valuable.
>
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk
Best Regards,
Alex
Message was edited by:
Alex Katykhin
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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{code}
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DB Name DB Id Instance Inst Num Release Cluster Host
ICAI 1504443695 icai 1 9.2.0.8.0 NO icaidb.icai.
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~~~~~~~~~~~~~~~~~
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-> ordered by wait time desc, waits desc (idle events last)
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log file switch (checkpoint 35,936 35,886 35,100 977 5.3
enqueue 6,144 5,660 16,684 2716 0.9
buffer busy waits 17,190 5,325 13,346 776 2.5
wait for a undo record 51,967 49,137 4,931 95 7.6
ARCH wait on SENDREQ 877 0 4,813 5489 0.1
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db file sequential read 600,718 0 621 1 88.1
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log file parallel write 7,052 0 421 60 1.0
log buffer space 1,361 16 230 169 0.2
db file scattered read 289,115 0 212 1 42.4
switch logfile command 116 23 160 1377 0.0
wait for stopper event to be 1,924 1,111 123 64 0.3
control file parallel write 1,355 0 63 46 0.2
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7,275 7,272 1.0 0.00 0.34 3716207873
update seq$ set increment$=:2,minvalue=:3,maxvalue=:4,cycle#=:5,
order$=:6,cache=:7,highwater=:8,audit$=:9,flags=:10 where obj#=:
1
6,293 6,283 1.0 0.00 0.00 2804237544
SELECT DECODE(:b1,'L',DECODE(:b2,'ENG',CITY_NAME,CITY_BL_NAME),D
ECODE(:b2,'ENG',CITY_SHORT_NAME,CITY_BL_SHORT_NAME)) CITY_NAME,C
ITY_TALUK_CODE,CITY_DIST_CODE,CITY_STATE_CODE,CITY_REGION_CODE,C
ITY_FRZ_FLAG_NUM FROM OM_CITY WHERE CITY_CODE = :b4
6,221 6,221 1.0 0.00 0.00 484036617
SELECT DAH_SYS_ID.NEXTVAL FROM DUAL
6,221 6,221 1.0 0.00 0.00 2945494810
SELECT COUNT(DAH_SYS_ID) FROM OT_DAK_ACTV_HISTORY WHERE DAH_ACTV
TYPE = :B2 AND DAHTXN_SYS_ID = :B1
5,979 5,979 1.0 0.00 0.00 35936114
SELECT STUD_DOC_STATUS FROM OM_STUDENT_HEAD WHERE STUD_SYS_ID
= :b1
4,637 4,637 1.0 0.00 0.00 1237293873
SELECT DECODE(:b1,'L',DECODE(:b2,'ENG',COU_NAME,COU_BL_NAME),DEC
ODE(:b2,'ENG',COU_SHORT_NAME,COU_BL_SHORT_NAME)) COU_NAME,COU_FR
Z_FLAG_NUM FROM OM_COUNTRY WHERE COU_CODE = :b4
4,404 1,276 0.3 0.00 0.00 1829426463
SELECT NVL(TAU_FROM_VALUE,0), NVL(TAU_TO_VALUE,0) FROM IM_TXN_AU
TH_USER WHERE TAU_TA_TYPE = :B3 AND TAU_TXN_CODE = :B2 AND TAU_A
UTH_UID = :B1
4,220 4,220 1.0 0.00 0.00 1006906503
UPDATE OT_DAK_ACTV_HISTORY SET DAH_ACTV_ED_DT = :B3 , DAH_ACTV_S
TATUS = 'C' WHERE DAH_ACTV_TYPE = :B2 AND DAH_TXN_SYS_ID = :B1
3,874 66 0.0 0.00 0.00 4284733339
SELECT TIT_NAME ||' '|| AR_FIRST_NAME||' '||AR_MIDDLE_NAME||' '|
|AR_SUR_NAME FROM OT_ARTICLE_REGISTRATION, OM_TITLE WHERE TRIM(A
SQL ordered by Executions for DB: ICAI Instance: icai Snaps: 70 -73
-> End Executions Threshold: 100 -
Log file switch (checkpoint incomplete)
hello,
Lately, I have a lot of update/delete work on my OLTP production database. Generally this database is heavy loaded with much inserts especially at the daytime so I do my work at nights :) However, this work cause some contention. I have run AWR raport and I see "log file switch (checkpoint incomplete)" on a second place in wait events. I have a six redo log groups, each file 400MB, redo log buffer 12MB, mttr 0, checkpoint interval 0 and checkpoint timeout 1800 so checkpoints are usually "made by" log switches. Normally I have 2-5 switches per hour, but when I am doing my work it's abut 15-20 switches/hour. Can I speed it up by resizing redo files or by adding more groups ? I don't have test environment to test it so I am wondering if somone has experiense with that?
thanks
10gr2, linuxHi Helter,
i have expirienced the same problem only with smaller log files and 3 groups, the solution you suggested helped me solve the issue, eversince i don't have any "checkpoint incomplete" error masaages in the alert log file.
i have enlarged each group to be 100 mb (initially was 50 mb) and added 2 more groups.
hope this solution will help you too.
dBarak -
RAC 10.2.0.4, event gc cr block busy & log file switch
hello everybody,
i would like to know if there is any dependencies between gc cr block busy and log switch in the one node of the rac cluster.
i had a select and its completion time lasted 12 secs instead of 1, the start time of the select is the start time of the log switch on the node.
But when i looked into the active session history the session which was standing for that select had been waiting gc cr block busy instead log file switch completion.
While looking to the Google resources i ve noticed that "The gc current block busy and gc cr block busy wait events indicate that the
remote instance received the block after a remote instance processing delay.
In most cases, this is due to a log flush".
I would be really greatfull if anybody would be able to locate the initial dependancy i ve mantioned and explain the cause of the issue as i can not quite get why the selection took so long.
Thank you in advance!Did you told "log file switch"?
you mean log file switch (checkpoint incomplete) or log file switch (archiving needed) or log file switch/archive or log file switch (clearing log file) or log file switch completion or log switch/archive
however a instance can wait ... if you find high values about waiting, you may tune your database.
please show us
- Top 5 Wait Events
SQL> alter session set nls_date_format='YYYY/MM/DD HH24:MI:SS';
SQL> select name, completion_time from V$ARCHIVED_LOG order by completion_time ;
Check How often do you switch logfile to archive log? ... Every switch log file... you may find "log file switch" waiting
I see... you no high DML activitiy.
But Please check High segment + object and query on AWR report... (example: Segments by Physical Writes )
just investigate
Good Luck -
Log file switch (archiving needed)
Hi,
My database is on windows 2003, 10.2.0.4, recently I have been getting the following wait events on a regular basis, LOG FILE SWITCH (ARCHIVING NEEDED)...My redo files are 50MB with 5 groups...I have changed the log_archive_max_process from 2 to 3, but still the problem persists...can anyone help me regarding the same?As to what other changes can be done?and this happens only during the time of BOD and EOD.
Thanks,
AJHi Jonathan,
Thanks for the reply, I am not worried abt the archiving thing for the time being,as my database was working absolutely fine before the new query that was added in the Begin of Day process. So I am trying to tweak the query.
Folllowing is the procedure which gets called during the Begin of Day:
CREATE OR REPLACE procedure Lms_Pr_Bod_Update_Tmp (p_import_type in number)
as
v_update_script varchar2(2000);
v_upper_start_tag varchar2(10); -- san_22-apr-2009
v_upper_end_tag varchar2(10); -- san_22-apr-2009
begin
declare
cursor cur_update_tmp is
select -- this query is for all of lov type of data
a.destination_column_name, a.column_to_update , b.mapped_lov_syscode lov_syscode,
c.destination_table_name,'LOV_DATA_SYSCODE' select_attribute,'LMS_LOV_DATA_MAP' select_table,
'SOURCE_UNIQUE_ID' where_condition,'LOV_SYSCODE' lov_condition,'LOV' att_type
from lms_import_column_info a
inner join lms_attribute_master b
on a.attribute_syscode = b.attribute_syscode
and (a.column_to_update is not null or trim(a.column_to_update) = '')
inner join lms_import_type_master c
on a.import_type_syscode = c.import_type_syscode
where a.import_type_syscode = p_import_type
and b.mapped_lov_syscode is not null
union all
select -- this query is for all of dummy attribute
a.destination_column_name, a.column_to_update , 1 lov_syscode,
d.destination_table_name,c.attribute_name_internal select_attribute,
case
when b.applicable_for = 'INS' then 'LMS_ENTITY_INSTRUMENT'
when b.applicable_for = 'ACC' then 'LMS_ENTITY_ACCOUNT'
end case,
b.attribute_name_internal where_condition,'1' lov_condition,'DUMMY' att_type
from lms_import_column_info a
inner join lms_attribute_master b
on a.attribute_syscode = b.attribute_syscode
and (a.column_to_update is not null and trim(a.column_to_update) <> ' ')
and b.attribute_type = 'DUM' and dummy_column_type = 'FILT'
inner join lms_attribute_master c
on b.dummy_mapped_attribute_pk = c.attribute_syscode
inner join lms_import_type_master d
on a.import_type_syscode = d.import_type_syscode
where a.import_type_syscode = p_import_type;
begin
v_upper_start_tag := 'UPPER('; -- san_22-apr-2009
v_upper_end_tag := ')'; -- san_22-apr-2009
for cr_update_tmp in cur_update_tmp loop
if p_import_type = 4 and cr_update_tmp.column_to_update IN ('INSTRUMENT_SYSCODE','ACCOUNT_SYSCODE')
and Upper(cr_update_tmp.destination_table_name) = 'LMS_ENTITY_TRANSACTION_TMP' then
v_upper_start_tag := ''; -- san_22-apr-2009
v_upper_end_tag := ''; -- san_22-apr-2009
end if;
v_update_script := 'UPDATE ' || cr_update_tmp.destination_table_name || ' A SET ' || ' A.' || cr_update_tmp.column_to_update || ' =
(select ' || CR_UPDATE_TMP.SELECT_ATTRIBUTE || ' from ' || CR_UPDATE_TMP.SELECT_TABLE || '
where ' || V_UPPER_START_TAG || CR_UPDATE_TMP.WHERE_CONDITION || V_UPPER_END_TAG || '=' || V_UPPER_START_TAG || CR_UPDATE_TMP.DESTINATION_COLUMN_NAME || V_UPPER_END_TAG ||
' AND ' || cr_update_tmp.lov_condition || ' = ' || cr_update_tmp.lov_syscode || ')';
v_upper_start_tag := 'UPPER('; v_upper_end_tag := ')';
execute immediate (v_update_script);
end loop;
end;
end;
Following is the flow of the query:
1. A temporary table is created where in the updates can be made.
2. Rows are inserted into ths table from the source table
3. Updates are performed on this table
4. Updates are then copied to the source table
5. This procedure is alled twice, so before getting called for the second time, table is truncated.
Thanks,
AJ -
WARNING - Last redo log file switch interval was 6 minutes. Next interval p
Hello!
I just started monitoring my Oracle via ConSol Nagios script.
Now it show`s a Warning because:
WARNING - Last redo log file switch interval was 6 minutes. Next interval presumably >2 minutes. Second incident in a row.
As I do not know much about Oracle I do not understand that message.
a) What does it mean ?
b) Is it really critical ?
Thanks!>
I just started monitoring my Oracle via ConSol Nagios script.
Now it show`s a Warning because:
WARNING - Last redo log file switch interval was 6 minutes. Next interval presumably >2 minutes. Second incident in a row.
As I do not know much about Oracle I do not understand that message.
a) What does it mean ?
b) Is it really critical ?
>
First of all: This is not an Oracle Error message. Instead, you have a somewhat arbitrarily threshold set in your non-Oracle monitoring tool. If this happens only once in a while - ignore it or modify the threshold.
Generally, frequent fast logswitches can be the cause of performance problems.
If you have Oracle Enterprise Manager in place and Diagnostic Pack licensed, it would give you a much more qualified statement about your Database performance. Also a recommendation to increase the Logfile size in case.
If you look for a procedure to increase the size of your logfiles:
http://uhesse.wordpress.com/2010/01/20/how-to-change-the-size-of-online-redologs/
Kind regards
Uwe Hesse
http://uhesse.wordpress.com -
Hi,
on 11g R2, on Win 2008, how to see the frequency of switching from one log file to another ?
Thank you.you can use this:
select to_char(first_time,'YYYY-MON-DD') day,
to_char(sum(decode(to_char(first_time,'HH24'),'00',1,0)),'99') "00",
to_char(sum(decode(to_char(first_time,'HH24'),'01',1,0)),'99') "01",
to_char(sum(decode(to_char(first_time,'HH24'),'02',1,0)),'99') "02",
to_char(sum(decode(to_char(first_time,'HH24'),'03',1,0)),'99') "03",
to_char(sum(decode(to_char(first_time,'HH24'),'04',1,0)),'99') "04",
to_char(sum(decode(to_char(first_time,'HH24'),'05',1,0)),'99') "05",
to_char(sum(decode(to_char(first_time,'HH24'),'06',1,0)),'99') "06",
to_char(sum(decode(to_char(first_time,'HH24'),'07',1,0)),'99') "07",
to_char(sum(decode(to_char(first_time,'HH24'),'08',1,0)),'99') "08",
to_char(sum(decode(to_char(first_time,'HH24'),'09',1,0)),'99') "09",
to_char(sum(decode(to_char(first_time,'HH24'),'10',1,0)),'99') "10",
to_char(sum(decode(to_char(first_time,'HH24'),'11',1,0)),'99') "11",
to_char(sum(decode(to_char(first_time,'HH24'),'12',1,0)),'99') "12",
to_char(sum(decode(to_char(first_time,'HH24'),'13',1,0)),'99') "13",
to_char(sum(decode(to_char(first_time,'HH24'),'14',1,0)),'99') "14",
to_char(sum(decode(to_char(first_time,'HH24'),'15',1,0)),'99') "15",
to_char(sum(decode(to_char(first_time,'HH24'),'16',1,0)),'99') "16",
to_char(sum(decode(to_char(first_time,'HH24'),'17',1,0)),'99') "17",
to_char(sum(decode(to_char(first_time,'HH24'),'18',1,0)),'99') "18",
to_char(sum(decode(to_char(first_time,'HH24'),'19',1,0)),'99') "19",
to_char(sum(decode(to_char(first_time,'HH24'),'20',1,0)),'99') "20",
to_char(sum(decode(to_char(first_time,'HH24'),'21',1,0)),'99') "21",
to_char(sum(decode(to_char(first_time,'HH24'),'22',1,0)),'99') "22",
to_char(sum(decode(to_char(first_time,'HH24'),'23',1,0)),'99') "23"
from v$log_history group by to_char(first_time,'YYYY-MON-DD'); -
I was wondering how I could have my 10g archive log's perform a switch based on time and not size?
Do I have to schedule a job or set a parameter or ?
Thanks.you could create a jobI wouldn't advise this way, you can have nightly batches which manipulate too many data, in this case the automatic switch (managed by Oracle core) will allready more often, or during the day (open hours) if there are too many users (for one reason...) which work in same time and create a max of activities, with crontab job, you will have an overload of switch redolog... because scheduled switches by job can add to the automatic switches generated by Oracle. Your db will take the time to managed switches instead of a better job.
I wouldn't chocked if only two or three switches occured during an all unworked day (why switch if no activity, what did you want to save ?), and no surprise if switches every 5 min during batches.
Nicolas. -
Performance issues - Log file parallel write
Hi there,
Since a few months I have big performance issues with my Oracle 11.2.0.1.0.
If I look in the Enterprise manager (in blocking sessions) I see al lot of "log file paralles writes" and a lot of "log file sync" .
We have configured an active data guard environment and are using ASM.
We are not stressing out the database with heavy queries or commits or something, but sometimes during the day this happens on non specific times...
We've investigated everything (performance to SAN / heavy queries / oracle problems etc etc) and we really don't know what to do anymore so i thought.. let's try a post on the Forum.....
Perhaps someone had similar things?
Thanks,
BR
Markmwevromans wrote:
See blow a tail of alertlog.
Tue Apr 24 15:12:17 2012
Thread 1 cannot allocate new log, sequence 194085
Checkpoint not complete
Current log# 1 seq# 194084 mem# 0: +DATA/kewillprd/onlinelog/group_1.262.712516155
Current log# 1 seq# 194084 mem# 1: +FRA/kewillprd/onlinelog/group_1.438.756466165
LGWR: Standby redo logfile selected to archive thread 1 sequence 194085
LGWR: Standby redo logfile selected for thread 1 sequence 194085 for destination LOG_ARCHIVE_DEST_2
Thread 1 advanced to log sequence 194085 (LGWR switch)
Current log# 2 seq# 194085 mem# 0: +DATA/kewillprd/onlinelog/group_2.264.712516155
Current log# 2 seq# 194085 mem# 1: +FRA/kewillprd/onlinelog/group_2.418.756466215
Tue Apr 24 15:12:21 2012
Archived Log entry 388061 added for thread 1 sequence 194084 ID 0x90d7aa62 dest 1:
Tue Apr 24 15:14:09 2012
Thread 1 cannot allocate new log, sequence 194086
Checkpoint not complete
Current log# 2 seq# 194085 mem# 0: +DATA/kewillprd/onlinelog/group_2.264.712516155
Current log# 2 seq# 194085 mem# 1: +FRA/kewillprd/onlinelog/group_2.418.756466215
LGWR: Standby redo logfile selected to archive thread 1 sequence 194086
LGWR: Standby redo logfile selected for thread 1 sequence 194086 for destination LOG_ARCHIVE_DEST_2
Thread 1 advanced to log sequence 194086 (LGWR switch)
Current log# 3 seq# 194086 mem# 0: +DATA/kewillprd/onlinelog/group_3.266.712516155
Current log# 3 seq# 194086 mem# 1: +FRA/kewillprd/onlinelog/group_3.435.756466241
Tue Apr 24 15:14:14 2012
Archived Log entry 388063 added for thread 1 sequence 194085 ID 0x90d7aa62 dest 1:
Tue Apr 24 15:16:46 2012
Thread 1 cannot allocate new log, sequence 194087
Checkpoint not complete
Current log# 3 seq# 194086 mem# 0: +DATA/kewillprd/onlinelog/group_3.266.712516155
Current log# 3 seq# 194086 mem# 1: +FRA/kewillprd/onlinelog/group_3.435.756466241
Thread 1 cannot allocate new log, sequence 194087
Private strand flush not complete
Current log# 3 seq# 194086 mem# 0: +DATA/kewillprd/onlinelog/group_3.266.712516155
Current log# 3 seq# 194086 mem# 1: +FRA/kewillprd/onlinelog/group_3.435.756466241
LGWR: Standby redo logfile selected to archive thread 1 sequence 194087
LGWR: Standby redo logfile selected for thread 1 sequence 194087 for destination LOG_ARCHIVE_DEST_2
Thread 1 advanced to log sequence 194087 (LGWR switch)
Current log# 1 seq# 194087 mem# 0: +DATA/kewillprd/onlinelog/group_1.262.712516155
Current log# 1 seq# 194087 mem# 1: +FRA/kewillprd/onlinelog/group_1.438.756466165
Tue Apr 24 15:16:54 2012
Archived Log entry 388065 added for thread 1 sequence 194086 ID 0x90d7aa62 dest 1:
Tue Apr 24 15:18:59 2012
Thread 1 cannot allocate new log, sequence 194088
Checkpoint not complete
Current log# 1 seq# 194087 mem# 0: +DATA/kewillprd/onlinelog/group_1.262.712516155
Current log# 1 seq# 194087 mem# 1: +FRA/kewillprd/onlinelog/group_1.438.756466165
Thread 1 cannot allocate new log, sequence 194088
Private strand flush not complete
Current log# 1 seq# 194087 mem# 0: +DATA/kewillprd/onlinelog/group_1.262.712516155
Current log# 1 seq# 194087 mem# 1: +FRA/kewillprd/onlinelog/group_1.438.756466165
LGWR: Standby redo logfile selected to archive thread 1 sequence 194088
LGWR: Standby redo logfile selected for thread 1 sequence 194088 for destination LOG_ARCHIVE_DEST_2
Thread 1 advanced to log sequence 194088 (LGWR switch)
Current log# 2 seq# 194088 mem# 0: +DATA/kewillprd/onlinelog/group_2.264.712516155
Current log# 2 seq# 194088 mem# 1: +FRA/kewillprd/onlinelog/group_2.418.756466215
Tue Apr 24 15:19:06 2012
Archived Log entry 388067 added for thread 1 sequence 194087 ID 0x90d7aa62 dest 1:
Tue Apr 24 15:22:00 2012
Thread 1 cannot allocate new log, sequence 194089
Checkpoint not complete
Current log# 2 seq# 194088 mem# 0: +DATA/kewillprd/onlinelog/group_2.264.712516155
Current log# 2 seq# 194088 mem# 1: +FRA/kewillprd/onlinelog/group_2.418.756466215
Thread 1 cannot allocate new log, sequence 194089
Private strand flush not complete
Current log# 2 seq# 194088 mem# 0: +DATA/kewillprd/onlinelog/group_2.264.712516155
Current log# 2 seq# 194088 mem# 1: +FRA/kewillprd/onlinelog/group_2.418.756466215
LGWR: Standby redo logfile selected to archive thread 1 sequence 194089
LGWR: Standby redo logfile selected for thread 1 sequence 194089 for destination LOG_ARCHIVE_DEST_2
Thread 1 advanced to log sequence 194089 (LGWR switch)
Current log# 3 seq# 194089 mem# 0: +DATA/kewillprd/onlinelog/group_3.266.712516155
Current log# 3 seq# 194089 mem# 1: +FRA/kewillprd/onlinelog/group_3.435.756466241
Tue Apr 24 15:19:06 2012
Archived Log entry 388069 added for thread 1 sequence 194088 ID 0x90d7aa62 dest 1:Hi
1st switch time ==> Tue Apr 24 15:18:59 2012
2nd switch time ==> Tue Apr 24 15:19:06 2012
3rd switch time ==> Tue Apr 24 15:19:06 2012
Redo log file switch has good impact on the performance of the database. Frequent log switches may lead to the slowness of the database . Oracle documents suggests to resize the redolog files so that log switches happen more like every 15-30 min (roughly depending on the architecture and recovery requirements).
AS i check the alertlog file and find that the log are switchinh very fequent which is one of the reason that you are getting checkpoint not complete message . i have face this issue many times and i generally increase the size of the logfile and set the archive_lag_time parameter as i have suggested above . If you further want to go root cause and more details then above guys will help you more because i don't have much experience in database tunning . If you looking for aworkarounf then you must go through it .
Good Luck
--neeraj -
Private strand flush not complete how to find optimal size of redo log file
hi,
i am using oracle 10.2.0 on unix system and getting Private strand flush not complete in the alert log file. i know this is due to check point is not completed.
I need to increase the size of redo log files or add new group to the database. i have log file switch (checkpoint incomplete) in the top 5 wait event.
i can't change any parameter of database. i have three redo log group and log files are of 250MB size. i want to know the suitable size to avoid problem.
select * from v$instance_recovery;
RECOVERY_ESTIMATED_IOS ACTUAL_REDO_BLKS TARGET_REDO_BLKS LOG_FILE_SIZE_REDO_BLKS LOG_CHKPT_TIMEOUT_REDO_BLKS LOG_CHKPT_INTERVAL_REDO_BLKS FAST_START_IO_TARGET_REDO_BLKS TARGET_MTTR ESTIMATED_MTTR CKPT_BLOCK_WRITES OPTIMAL_LOGFILE_SIZE ESTD_CLUSTER_AVAILABLE_TIME WRITES_MTTR WRITES_LOGFILE_SIZE WRITES_LOG_CHECKPOINT_SETTINGS WRITES_OTHER_SETTINGS WRITES_AUTOTUNE WRITES_FULL_THREAD_CKPT
625 9286 9999 921600 9999 0 9 112166207 0 0 219270206 0 3331591 5707793please suggest me or tell me the way how to find out suitable size to avoid problem.
thanks
umeshHow often should a database archive its logs
Re: Redo log size increase and performance
Please read the above thread and great replies by HJR sir. I think if you wish to get concept knowledge, you should add in your notes.
"If the FAST_START_MTTR_TARGET parameter is set to limit the instance recovery time, Oracle automatically tries to checkpoint as frequently as necessary. Under this condition, the size of the log files should be large enough to avoid additional checkpointing due to under sized log files. The optimal size can be obtained by querying the OPTIMAL_LOGFILE_SIZE column from the V$INSTANCE_RECOVERY view. You can also obtain sizing advice on the Redo Log Groups page of Oracle Enterprise Manager Database Control."
Source:http://download-west.oracle.com/docs/cd/B13789_01/server.101/b10752/build_db.htm#19559
Pl also see ML Doc 274264.1 (REDO LOGS SIZING ADVISORY) on tips to calculate the optimal size for redo logs in 10g databases
Source:Re: Redo Log Size in R12
HTH
Girish Sharma -
Hi All,
Oracle 10.2.0.4 on RHEL5.
We were getting "checkpoint not complete, Thread 1 cannot allocated new log..." in alert log. Also log switches were every 3/4 mins on Night batch updates.
Log file switch completion waits was high with average 30ms.
My redo logs and control files shared the same mount point.
Steps taken;
1> Relocated the redo logs to a different mount point. (So
2> Resized the redologs to 1G. (Current value was 150M).
..The value I derived after setting the fast_start_mttr_target..and checking the optimal_size (it was 900M)
Impact;
In day-time OLTP some transactions taking longer time.
Please advice...user13355115 wrote:
Hi All,
Oracle 10.2.0.4 on RHEL5.
We were getting "checkpoint not complete, Thread 1 cannot allocated new log..." in alert log. Also log switches were every 3/4 mins on Night batch updates.
Log file switch completion waits was high with average 30ms.
My redo logs and control files shared the same mount point.
Steps taken;
1> Relocated the redo logs to a different mount point. (So
2> Resized the redologs to 1G. (Current value was 150M).
..The value I derived after setting the fast_start_mttr_target..and checking the optimal_size (it was 900M)
Impact;
In day-time OLTP some transactions taking longer time.What caused the change in behavior in some OLTP transactions.
Consider enabling SQL_TRACE to see where actual time is being spent.
Thread: HOW TO: Post a SQL statement tuning request - template posting
HOW TO: Post a SQL statement tuning request - template posting -
Hi,
I have a very light application in Oracle 9.2.0.7 in Linux-32bits that is generating 400 logfiles a day. I can´t find why those logs are being generated!
The only thing relevant in that application is a big table that serves only for insert command (1000 per hour) for audit reasons. But this table was created with NOLOGGING option.
Redo Size: 4 groups of 40 Mb each.
The insert statement uses a sequence to generate a unique key. Is this sequence causing my big logfile generation?
Thanks,
Paulo.Here is the statspack:
STATSPACK report for
DB Name DB Id Instance Inst Num Release Cluster Host
DB 378381468 DB 1 9.2.0.7.0 NO host
Snap Id Snap Time Sessions Curs/Sess Comment
Begin Snap: 12 28-Jun-07 11:05:11 26 1,198.7
End Snap: 13 28-Jun-07 12:05:24 29 1,077.2
Elapsed: 60.22 (mins)
Cache Sizes (end)
~~~~~~~~~~~~~~~~~
Buffer Cache: 512M Std Block Size: 8K
Shared Pool Size: 512M Log Buffer: 5,120K
Load Profile
~~~~~~~~~~~~ Per Second Per Transaction
Redo size: 281,252.38 2,073.48
Logical reads: 73,113.76 539.02
Block changes: 3,133.29 23.10
Physical reads: 3.24 0.02
Physical writes: 21.39 0.16
User calls: 26.12 0.19
Parses: 145.64 1.07
Hard parses: 0.81 0.01
Sorts: 138.33 1.02
Logons: 0.69 0.01
Executes: 443.27 3.27
Transactions: 135.64
% Blocks changed per Read: 4.29 Recursive Call %: 98.97
Rollback per transaction %: 0.13 Rows per Sort: 17.26
Instance Efficiency Percentages (Target 100%)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Buffer Nowait %: 99.99 Redo NoWait %: 100.00
Buffer Hit %: 100.00 In-memory Sort %: 99.99
Library Hit %: 99.66 Soft Parse %: 99.44
Execute to Parse %: 67.14 Latch Hit %: 99.93
Parse CPU to Parse Elapsd %: 55.03 % Non-Parse CPU: 99.22
Shared Pool Statistics Begin End
Memory Usage %: 91.06 91.23
% SQL with executions>1: 44.54 39.78
% Memory for SQL w/exec>1: 43.09 33.89
Top 5 Timed Events
~~~~~~~~~~~~~~~~~~ % Total
Event Waits Time (s) Ela Time
CPU time 3,577 84.73
log file parallel write 854,726 359 8.51
row cache lock 56,780 104 2.47
process startup 172 91 2.16
SQL*Net message from dblink 5,001 22 .53
Wait Events for DB: DB Instance: DB Snaps: 12 -13
-> 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
log file parallel write 854,726 0 359 0 1.7
row cache lock 56,780 0 104 2 0.1
process startup 172 4 91 530 0.0
SQL*Net message from dblink 5,001 0 22 4 0.0
log file sync 3,015 3 19 6 0.0
enqueue 471 1 9 20 0.0
buffer busy waits 20,290 0 8 0 0.0
db file sequential read 3,853 0 6 2 0.0
SQL*Net more data from dblin 88,584 0 5 0 0.2
control file parallel write 1,704 0 5 3 0.0
latch free 1,404 748 4 3 0.0
single-task message 134 0 4 27 0.0
LGWR wait for redo copy 8,230 1 2 0 0.0
log file switch completion 60 0 2 32 0.0
log file sequential read 1,333 0 2 1 0.0
control file sequential read 4,530 0 1 0 0.0
db file scattered read 246 0 0 1 0.0
SQL*Net more data to client 7,292 0 0 0 0.0
SQL*Net break/reset to clien 72 0 0 1 0.0
db file parallel write 4,568 0 0 0 0.0
log file single write 62 0 0 0 0.0
async disk IO 3,410 0 0 0 0.0
SQL*Net message to dblink 5,001 0 0 0 0.0
direct path read (lob) 84 0 0 0 0.0
direct path read 318 0 0 0 0.0
direct path write 312 0 0 0 0.0
buffer deadlock 115 115 0 0 0.0
SQL*Net message from client 86,475 0 27,758 321 0.2
jobq slave wait 4,594 4,532 13,455 2929 0.0
SQL*Net more data from clien 602 0 1 2 0.0
SQL*Net message to client 86,481 0 0 0 0.2
Background Wait Events for DB: DB Instance: DB Snaps: 12 -13
-> 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 854,744 0 359 0 1.7
control file parallel write 1,704 0 5 3 0.0
LGWR wait for redo copy 8,230 1 2 0 0.0
log file sequential read 1,333 0 2 1 0.0
control file sequential read 1,849 0 1 1 0.0
db file parallel write 4,567 0 0 0 0.0
latch free 74 0 0 0 0.0
rdbms ipc reply 65 0 0 0 0.0
log file single write 62 0 0 0 0.0
async disk IO 3,410 0 0 0 0.0
db file sequential read 1 0 0 8 0.0
buffer busy waits 5 0 0 0 0.0
direct path read 248 0 0 0 0.0
direct path write 248 0 0 0 0.0
rdbms ipc message 868,357 6,776 30,095 35 1.8
pmon timer 1,204 1,204 3,529 2931 0.0
smon timer 154 0 3,514 22816 0.0
Instance Activity Stats for DB: DB Instance: DB Snaps: 12 -13
Statistic Total per Second per Trans
active txn count during cleanout 2,844 0.8 0.0
background checkpoints completed 31 0.0 0.0
background checkpoints started 31 0.0 0.0
background timeouts 7,956 2.2 0.0
branch node splits 15 0.0 0.0
buffer is not pinned count 324,721,116 89,875.8 662.6
buffer is pinned count 308,901,876 85,497.3 630.3
bytes received via SQL*Net from c 8,048,130 2,227.6 16.4
bytes received via SQL*Net from d 181,575,342 50,256.1 370.5
bytes sent via SQL*Net to client 33,964,494 9,400.6 69.3
bytes sent via SQL*Net to dblink 933,170 258.3 1.9
calls to get snapshot scn: kcmgss 9,900,434 2,740.2 20.2
calls to kcmgas 985,222 272.7 2.0
calls to kcmgcs 11,669 3.2 0.0
change write time 9,910 2.7 0.0
cleanout - number of ktugct calls 18,903 5.2 0.0
cleanouts and rollbacks - consist 33 0.0 0.0
cleanouts only - consistent read 932 0.3 0.0
cluster key scan block gets 289,955 80.3 0.6
cluster key scans 101,840 28.2 0.2
commit cleanout failures: block l 0 0.0 0.0
commit cleanout failures: buffer 113 0.0 0.0
commit cleanout failures: callbac 96 0.0 0.0
commit cleanout failures: cannot 3,095 0.9 0.0
commit cleanouts 1,966,376 544.3 4.0
commit cleanouts successfully com 1,963,072 543.3 4.0
commit txn count during cleanout 309,283 85.6 0.6
consistent changes 5,245,452 1,451.8 10.7
consistent gets 242,967,989 67,248.3 495.8
consistent gets - examination 135,768,580 37,577.8 277.0
CPU used by this session 357,659 99.0 0.7
CPU used when call started 344,951 95.5 0.7
CR blocks created 768 0.2 0.0
current blocks converted for CR 0 0.0 0.0
cursor authentications 886 0.3 0.0
data blocks consistent reads - un 1,760 0.5 0.0
db block changes 11,320,580 3,133.3 23.1
db block gets 21,192,200 5,865.5 43.2
DBWR buffers scanned 0 0.0 0.0
DBWR checkpoint buffers written 69,649 19.3 0.1
DBWR checkpoints 31 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 revisited being-written buff 0 0.0 0.0
DBWR summed scan depth 0 0.0 0.0
DBWR transaction table writes 2,070 0.6 0.0
DBWR undo block writes 44,323 12.3 0.1
deferred (CURRENT) block cleanout 745,333 206.3 1.5
dirty buffers inspected 1 0.0 0.0
enqueue conversions 8,193 2.3 0.0
enqueue deadlocks 1 0.0 0.0
enqueue releases 2,002,960 554.4 4.1
enqueue requests 2,002,963 554.4 4.1
enqueue timeouts 3 0.0 0.0
enqueue waits 451 0.1 0.0
Instance Activity Stats for DB: DB Instance: DB Snaps: 12 -13
Statistic Total per Second per Trans
exchange deadlocks 115 0.0 0.0
execute count 1,601,528 443.3 3.3
free buffer inspected 30 0.0 0.0
free buffer requested 1,196,628 331.2 2.4
hot buffers moved to head of LRU 26,707 7.4 0.1
immediate (CR) block cleanout app 965 0.3 0.0
immediate (CURRENT) block cleanou 10,817 3.0 0.0
index fast full scans (full) 0 0.0 0.0
index fetch by key 131,028,270 36,265.8 267.4
index scans kdiixs1 17,868,907 4,945.7 36.5
leaf node splits 4,528 1.3 0.0
leaf node 90-10 splits 3,017 0.8 0.0
logons cumulative 2,499 0.7 0.0
messages received 859,631 237.9 1.8
messages sent 859,631 237.9 1.8
no buffer to keep pinned count 21,253 5.9 0.0
no work - consistent read gets 87,667,752 24,264.5 178.9
opened cursors cumulative 528,984 146.4 1.1
OS Involuntary context switches 0 0.0 0.0
OS Page faults 0 0.0 0.0
OS Page reclaims 0 0.0 0.0
OS System time used 0 0.0 0.0
OS User time used 0 0.0 0.0
OS Voluntary context switches 0 0.0 0.0
parse count (failures) 7 0.0 0.0
parse count (hard) 2,928 0.8 0.0
parse count (total) 526,209 145.6 1.1
parse time cpu 2,778 0.8 0.0
parse time elapsed 5,048 1.4 0.0
physical reads 11,690 3.2 0.0
physical reads direct 6,698 1.9 0.0
physical reads direct (lob) 102 0.0 0.0
physical writes 77,270 21.4 0.2
physical writes direct 7,620 2.1 0.0
physical writes direct (lob) 0 0.0 0.0
physical writes non checkpoint 33,360 9.2 0.1
pinned buffers inspected 0 0.0 0.0
prefetched blocks 799 0.2 0.0
prefetched blocks aged out before 0 0.0 0.0
process last non-idle time 3,630 1.0 0.0
recursive calls 9,053,277 2,505.8 18.5
recursive cpu usage 255,973 70.9 0.5
redo blocks written 2,572,625 712.1 5.3
redo buffer allocation retries 50 0.0 0.0
redo entries 3,074,994 851.1 6.3
redo log space requests 60 0.0 0.0
redo log space wait time 193 0.1 0.0
redo ordering marks 0 0.0 0.0
redo size 1,016,164,852 281,252.4 2,073.5
redo synch time 1,956 0.5 0.0
redo synch writes 5,317 1.5 0.0
redo wastage 259,689,040 71,876.3 529.9
redo write time 37,488 10.4 0.1
redo writer latching time 242 0.1 0.0
redo writes 854,744 236.6 1.7
rollback changes - undo records a 1,098 0.3 0.0
Instance Activity Stats for DB: DB Instance: DB Snaps: 12 -13
Statistic Total per Second per Trans
rollbacks only - consistent read 747 0.2 0.0
rows fetched via callback 117,908,375 32,634.5 240.6
session connect time 0 0.0 0.0
session cursor cache count 16 0.0 0.0
session cursor cache hits 484,372 134.1 1.0
session logical reads 264,160,020 73,113.8 539.0
session pga memory 16,473,320 4,559.5 33.6
session pga memory max 16,914,080 4,681.5 34.5
session uga memory 17,216,514,728 4,765,157.7 35,130.3
session uga memory max 1,865,036,296 516,201.6 3,805.6
shared hash latch upgrades - no w 17,251,803 4,774.9 35.2
shared hash latch upgrades - wait 24,671 6.8 0.1
sorts (disk) 32 0.0 0.0
sorts (memory) 499,747 138.3 1.0
sorts (rows) 8,626,333 2,387.6 17.6
SQL*Net roundtrips to/from client 80,069 22.2 0.2
SQL*Net roundtrips to/from dblink 5,001 1.4 0.0
summed dirty queue length 0 0.0 0.0
switch current to new buffer 1 0.0 0.0
table fetch by rowid 238,882,317 66,117.4 487.4
table fetch continued row 4,436,670 1,228.0 9.1
table scan blocks gotten 5,066,302 1,402.2 10.3
table scan rows gotten 134,679,712 37,276.4 274.8
table scans (direct read) 0 0.0 0.0
table scans (long tables) 447 0.1 0.0
table scans (short tables) 152,382 42.2 0.3
transaction rollbacks 530 0.2 0.0
transaction tables consistent rea 0 0.0 0.0
transaction tables consistent rea 0 0.0 0.0
user calls 94,382 26.1 0.2
user commits 489,423 135.5 1.0
user rollbacks 653 0.2 0.0
write clones created in backgroun 11 0.0 0.0
write clones created in foregroun 878 0.2 0.0
Tablespace IO Stats for DB: DB Instance: DB Snaps: 12 -13
->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)
T1_UNDO
31 0 0.0 1.0 46,535 13 344 0.4
T1
31 0 0.0 1.0 13,754 4 3,657 0.4
T2
3,308 1 0.8 1.1 2,973 1 0 0.0
T3
31 0 0.0 1.0 5,710 2 16,240 0.4
T4
555 0 4.0 1.0 600 0 0 0.0
SYSTEM
429 0 3.9 2.5 280 0 49 0.2
TEMP
134 0 0.4 48.1 238 0 0 0.0
T1_16K
31 0 0.0 1.0 31 0 0 0.0
T2_16K
31 0 0.0 1.0 31 0 0 0.0
Buffer Pool Statistics for DB: DB Instance: DB Snaps: 12 -13
-> 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 49,625 100.0 263,975,320 4,909 69,666 0 0 20,290
16k 7,056 100.0 30 0 0 0 0 0
Instance Recovery Stats for DB: DB Instance: DB Snaps: 12 -13
-> 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 0 0 10518 10000 73728 186265 10000
E 0 0 13189 10000 73728 219498 10000
Buffer Pool Advisory for DB: DB Instance: DB End Snap: 13
-> 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 32 .1 3,970 205.60 4,726,309,734
D 64 .2 7,940 111.86 2,571,419,284
D 96 .2 11,910 59.99 1,379,092,849
D 128 .3 15,880 32.24 741,224,090
D 160 .4 19,850 16.05 369,050,333
D 192 .5 23,820 1.28 29,352,221
D 224 .6 27,790 1.05 24,077,507
D 256 .6 31,760 1.03 23,723,389
D 288 .7 35,730 1.02 23,518,434
D 320 .8 39,700 1.01 23,328,106
D 352 .9 43,670 1.01 23,193,257
D 384 1.0 47,640 1.00 23,064,957
D 400 1.0 49,625 1.00 22,987,576
D 416 1.0 51,610 1.00 22,927,325
D 448 1.1 55,580 0.99 22,824,032
D 480 1.2 59,550 0.99 22,713,509
D 512 1.3 63,520 0.99 22,649,147
D 544 1.4 67,490 0.98 22,605,489
D 576 1.4 71,460 0.98 22,525,897
D 608 1.5 75,430 0.97 22,407,418
D 640 1.6 79,400 0.96 22,022,381
16k 16 .1 1,008 1.00 139,218,299
16k 32 .3 2,016 1.00 139,211,699
16k 48 .4 3,024 1.00 139,207,678
16k 64 .6 4,032 1.00 139,202,581
16k 80 .7 5,040 1.00 139,198,339
16k 96 .9 6,048 1.00 139,193,448
16k 112 1.0 7,056 1.00 139,188,446
16k 128 1.1 8,064 1.00 139,183,808
16k 144 1.3 9,072 1.00 139,179,598
16k 160 1.4 10,080 1.00 139,175,656
16k 176 1.6 11,088 1.00 139,170,607
16k 192 1.7 12,096 1.00 139,166,491
16k 208 1.9 13,104 1.00 139,162,487
16k 224 2.0 14,112 1.00 139,158,197
16k 240 2.1 15,120 1.00 139,153,797
16k 256 2.3 16,128 1.00 139,149,365
16k 272 2.4 17,136 1.00 139,144,252
16k 288 2.6 18,144 1.00 139,140,121
16k 304 2.7 19,152 1.00 139,135,435
16k 320 2.9 20,160 1.00 139,130,845
Buffer wait Statistics for DB: DB Instance: DB Snaps: 12 -13
-> ordered by wait time desc, waits desc
Tot Wait Avg
Class Waits Time (s) Time (ms)
data block 19,912 8 0
undo header 343 0 0
segment header 34 0 0
undo block 1 0 0
Enqueue activity for DB: DB Instance: DB Snaps: 12 -13
-> Enqueue stats gathered prior to 9i should not be compared with 9i data
-> ordered by Wait Time desc, Waits desc
Avg Wt Wait
Eq Requests Succ Gets Failed Gets Waits Time (ms) Time (s)
TM 981,781 981,773 0 7 1,365.43 10
TX 983,944 983,906 0 412 .59 0
HW 4,645 4,645 0 32 .09 0
Rollback Segment Stats for DB: DB Instance: DB Snaps: 12 -13
->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
0 155.0 0.00 0 0 0 0
1 202,561.0 0.00 31,178,710 40 2 3
2 191,044.0 0.00 30,067,156 23 2 6
3 195,891.0 0.00 30,470,548 39 1 3
4 203,928.0 0.00 31,822,638 38 2 5
5 196,386.0 0.00 -4,264,350,168 38 1 3
6 204,125.0 0.00 32,081,200 24 1 7
7 192,169.0 0.00 33,732,012 45 3 6
8 195,819.0 0.00 30,503,550 40 2 2
9 202,905.0 0.00 31,595,438 40 2 4
10 195,796.0 0.00 30,566,652 29 4 9
Rollback Segment Storage for DB: DB Instance: DB Snaps: 12 -13
->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 12,705,792 944,176 2,213,732,352
2 11,657,216 1,548,937 2,214,715,392
3 13,754,368 832,465 243,392,512
4 13,754,368 946,902 235,069,440
5 12,705,792 964,352 2,195,374,080
6 20,045,824 1,232,438 2,416,041,984
7 12,705,792 977,490 3,822,182,400
8 10,608,640 875,068 243,392,512
9 11,657,216 878,119 243,392,512
10 18,997,248 1,034,104 2,281,889,792
Undo Segment Summary for DB: DB Instance: DB Snaps: 12 -13
-> 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 44,441 ########## 47 2 0 0 0/0/0/0/0/0
Undo Segment Stats for DB: DB Instance: DB Snaps: 12 -13
-> 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
28-Jun 11:56 7,111 ######## 47 1 0 0 0/0/0/0/0/0
28-Jun 11:46 10,782 ######## 18 2 0 0 0/0/0/0/0/0
28-Jun 11:36 6,170 ######## 42 1 0 0 0/0/0/0/0/0
28-Jun 11:26 4,966 ######## 13 1 0 0 0/0/0/0/0/0
28-Jun 11:16 6,602 ######## 40 1 0 0 0/0/0/0/0/0
28-Jun 11:06 8,810 ######## 10 1 0 0 0/0/0/0/0/0
Latch Activity for DB: DB Instance: DB Snaps: 12 -13
->"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
active checkpoint queue 9,585 0.0 0.0 0 0
alert log latch 158 0.0 0 0
archive control 220 0.0 0 0
archive process latch 220 0.5 1.0 0 0
cache buffer handles 264,718 0.0 0.0 0 0
cache buffers chains 416,051,175 0.0 0.0 4 401,018 0.0
cache buffers lru chain 1,285,963 0.0 0.0 0 1,206,550 0.0
channel handle pool latc 4,927 0.0 0 0
channel operations paren 10,788 0.0 0 0
checkpoint queue latch 528,319 0.0 0.0 0 69,506 0.0
child cursor hash table 35,371 0.0 0 0
Consistent RBA 854,833 0.0 0.0 0 0
dml lock allocation 1,963,007 0.9 0.0 0 0
dummy allocation 4,995 0.0 0 0
enqueue hash chains 4,014,593 0.5 0.0 0 0
enqueues 94,666 0.0 0.0 0 0
event group latch 2,340 0.0 0 0
FAL request queue 72 0.0 0 0
FIB s.o chain latch 310 0.0 0 0
FOB s.o list latch 6,769 0.0 0 0
global tx hash mapping 10,388 0.0 0 0
hash table column usage 16 0.0 0 479 0.0
job workq parent latch 0 0 316 0.0
job_queue_processes para 116 0.0 0 0
ktm global data 200 0.0 0 0
lgwr LWN SCN 855,008 0.0 0.0 0 0
library cache 5,836,900 0.4 0.0 0 8,926 0.6
library cache load lock 468 0.0 0 0
library cache pin 3,510,695 0.0 0.0 0 0
library cache pin alloca 1,402,523 0.0 0.0 0 0
list of block allocation 6,115 0.0 0 0
loader state object free 620 0.0 0 0
message pool operations 262 0.0 0 0
messages 2,664,950 0.4 0.0 0 0
mostly latch-free SCN 856,000 0.1 0.0 0 0
multiblock read objects 3,184 0.0 0 0
ncodef allocation latch 57 0.0 0 0
object stats modificatio 8 0.0 0 0
post/wait queue 6,183 0.0 0 3,082 0.0
process allocation 4,677 0.0 0 2,340 0.0
process group creation 4,677 0.0 0 0
redo allocation 4,784,936 0.5 0.0 0 0
redo copy 0 0 3,081,261 0.3
redo writing 2,576,299 0.0 0.2 0 0
row cache enqueue latch 3,017,144 0.0 0.0 0 0
row cache objects 5,049,552 0.8 0.0 0 92 0.0
sequence cache 984,824 0.0 0.1 0 0
session allocation 110,417 0.0 0.0 0 0
session idle bit 205,319 0.0 0 0
session switching 57 0.0 0 0
Latch Activity for DB: DB Instance: DB Snaps: 12 -13
->"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
session timer 1,204 0.0 0 0
shared pool 2,409,725 0.1 0.1 0 0
simulator hash latch 7,439,429 0.0 0.0 0 0
simulator lru latch 202 0.0 0 128,961 0.2
sort extent pool 1,053 0.0 0 0
SQL memory manager worka 67 0.0 0 0
temp lob duration state 187 0.0 0 0
transaction allocation 7,290 0.0 0 0
transaction branch alloc 5,668 0.0 0 0
undo global data 3,002,808 0.4 0.0 0 0
user lock 8,642 0.0 0 0
Latch Sleep breakdown for DB: DB Instance: DB Snaps: 12 -13
-> ordered by misses desc
Get Spin &
Latch Name Requests Misses Sleeps Sleeps 1->4
cache buffers chains 416,051,175 197,296 750 196776/298/2
15/7/0
row cache objects 5,049,552 42,368 38 42330/38/0/0
/0
redo allocation 4,784,936 24,766 77 24697/61/8/0
/0
library cache 5,836,900 23,477 276 23207/264/6/
0/0
enqueue hash chains 4,014,593 21,061 26 21035/26/0/0
/0
dml lock allocation 1,963,007 17,887 16 17872/14/1/0
/0
undo global data 3,002,808 12,350 8 12342/8/0/0/
0
messages 2,664,950 10,131 5 10126/5/0/0/
0
shared pool 2,409,725 1,362 189 1175/185/2/0
/0
row cache enqueue latch 3,017,144 470 7 463/7/0/0/0
mostly latch-free SCN 856,000 434 1 433/1/0/0/0
library cache pin 3,510,695 345 4 341/4/0/0/0
sequence cache 984,824 53 4 49/4/0/0/0
library cache pin allocati 1,402,523 35 1 34/1/0/0/0
redo writing 2,576,299 5 1 4/1/0/0/0
archive process latch 220 1 1 0/1/0/0/0
Latch Miss Sources for DB: DB Instance: DB Snaps: 12 -13
-> only latches with sleeps are shown
-> ordered by name, sleeps desc
NoWait Waiter
Latch Name Where Misses Sleeps Sleeps
archive process latch kcrrpa 0 1 0
cache buffers chains kcbgtcr: fast path 0 346 188
cache buffers chains kcbgtcr: kslbegin excl 0 163 239
cache buffers chains kcbrls: kslbegin 0 86 170
cache buffers chains kcbget: pin buffer 0 53 49
cache buffers chains kcbgcur: kslbegin 0 44 20
cache buffers chains kcbnlc 0 38 22
cache buffers chains kcbget: exchange 0 8 16
cache buffers chains kcbchg: kslbegin: call CR 0 3 21
cache buffers chains kcbget: exchange rls 0 3 2
cache buffers chains kcbnew 0 3 0
cache buffers chains kcbbxsv 0 2 0
cache buffers chains kcbchg: kslbegin: bufs not 0 1 23
dml lock allocation ktaiam 0 13 1
dml lock allocation ktaidm 0 3 15
enqueue hash chains ksqgtl3 0 22 2
enqueue hash chains ksqrcl 0 4 24
library cache kglic 0 55 4
library cache kglhdgn: child: 0 42 86
library cache kglobpn: child: 0 26 32
library cache kglpndl: child: after proc 0 14 0
library cache kglpndl: child: before pro 0 13 73
library cache kglpin: child: heap proces 0 12 29
library cache kgllkdl: child: cleanup 0 11 4
library cache kglupc: child 0 4 7
library cache kgldti: 2child 0 2 4
library cache kglpnp: child 0 1 4
library cache pin kglpnal: child: alloc spac 0 3 3
library cache pin kglpndl 0 1 1
library cache pin alloca kglpnal 0 1 0
messages ksaamb: after wakeup 0 3 2
messages ksarcv 0 2 2
mostly latch-free SCN kcslcu3 0 1 1
redo allocation kcrfwr 0 74 8
redo allocation kcrfwi: more space 0 -
Log file sync top event during performance test -av 36ms
Hi,
During the performance test for our product before deployment into product i see "log file sync" on top with Avg wait (ms) being 36 which i feel is too high.
Avg
wait % DB
Event Waits Time(s) (ms) time Wait Class
log file sync 208,327 7,406 36 46.6 Commit
direct path write 646,833 3,604 6 22.7 User I/O
DB CPU 1,599 10.1
direct path read temp 1,321,596 619 0 3.9 User I/O
log buffer space 4,161 558 134 3.5 ConfiguratAlthough testers are not complaining about the performance of the appplication , we ,DBAs, are expected to be proactive about the any bad signals from DB.
I am not able to figure out why "log file sync" is having such slow response.
Below is the snapshot from the load profile.
Snap Id Snap Time Sessions Curs/Sess
Begin Snap: 108127 16-May-13 20:15:22 105 6.5
End Snap: 108140 16-May-13 23:30:29 156 8.9
Elapsed: 195.11 (mins)
DB Time: 265.09 (mins)
Cache Sizes Begin End
~~~~~~~~~~~ ---------- ----------
Buffer Cache: 1,168M 1,136M Std Block Size: 8K
Shared Pool Size: 1,120M 1,168M Log Buffer: 16,640K
Load Profile Per Second Per Transaction Per Exec Per Call
~~~~~~~~~~~~ --------------- --------------- ---------- ----------
DB Time(s): 1.4 0.1 0.02 0.01
DB CPU(s): 0.1 0.0 0.00 0.00
Redo size: 607,512.1 33,092.1
Logical reads: 3,900.4 212.5
Block changes: 1,381.4 75.3
Physical reads: 134.5 7.3
Physical writes: 134.0 7.3
User calls: 145.5 7.9
Parses: 24.6 1.3
Hard parses: 7.9 0.4
W/A MB processed: 915,418.7 49,864.2
Logons: 0.1 0.0
Executes: 85.2 4.6
Rollbacks: 0.0 0.0
Transactions: 18.4Some of the top background wait events:
^LBackground Wait Events DB/Inst: Snaps: 108127-108140
-> ordered by wait time desc, waits desc (idle events last)
-> Only events with Total Wait Time (s) >= .001 are shown
-> %Timeouts: value of 0 indicates value was < .5%. Value of null is truly 0
Avg
%Time Total Wait wait Waits % bg
Event Waits -outs Time (s) (ms) /txn time
log file parallel write 208,563 0 2,528 12 1.0 66.4
db file parallel write 4,264 0 785 184 0.0 20.6
Backup: sbtbackup 1 0 516 516177 0.0 13.6
control file parallel writ 4,436 0 97 22 0.0 2.6
log file sequential read 6,922 0 95 14 0.0 2.5
Log archive I/O 6,820 0 48 7 0.0 1.3
os thread startup 432 0 26 60 0.0 .7
Backup: sbtclose2 1 0 10 10094 0.0 .3
db file sequential read 2,585 0 8 3 0.0 .2
db file single write 560 0 3 6 0.0 .1
log file sync 28 0 1 53 0.0 .0
control file sequential re 36,326 0 1 0 0.2 .0
log file switch completion 4 0 1 207 0.0 .0
buffer busy waits 5 0 1 116 0.0 .0
LGWR wait for redo copy 924 0 1 1 0.0 .0
log file single write 56 0 1 9 0.0 .0
Backup: sbtinfo2 1 0 1 500 0.0 .0During a previous perf test , things didnt look this bad for "log file sync. Few sections from the comparision report(awrddprt.sql)
{code}
Workload Comparison
~~~~~~~~~~~~~~~~~~~ 1st Per Sec 2nd Per Sec %Diff 1st Per Txn 2nd Per Txn %Diff
DB time: 0.78 1.36 74.36 0.02 0.07 250.00
CPU time: 0.18 0.14 -22.22 0.00 0.01 100.00
Redo size: 573,678.11 607,512.05 5.90 15,101.84 33,092.08 119.13
Logical reads: 4,374.04 3,900.38 -10.83 115.14 212.46 84.52
Block changes: 1,593.38 1,381.41 -13.30 41.95 75.25 79.38
Physical reads: 76.44 134.54 76.01 2.01 7.33 264.68
Physical writes: 110.43 134.00 21.34 2.91 7.30 150.86
User calls: 197.62 145.46 -26.39 5.20 7.92 52.31
Parses: 7.28 24.55 237.23 0.19 1.34 605.26
Hard parses: 0.00 7.88 100.00 0.00 0.43 100.00
Sorts: 3.88 4.90 26.29 0.10 0.27 170.00
Logons: 0.09 0.08 -11.11 0.00 0.00 0.00
Executes: 126.69 85.19 -32.76 3.34 4.64 38.92
Transactions: 37.99 18.36 -51.67
First Second Diff
1st 2nd
Event Wait Class Waits Time(s) Avg Time(ms) %DB time Event Wait Class Waits Time(s) Avg Time
(ms) %DB time
SQL*Net more data from client Network 2,133,486 1,270.7 0.6 61.24 log file sync Commit 208,355 7,407.6
35.6 46.57
CPU time N/A 487.1 N/A 23.48 direct path write User I/O 646,849 3,604.7
5.6 22.66
log file sync Commit 99,459 129.5 1.3 6.24 log file parallel write System I/O 208,564 2,528.4
12.1 15.90
log file parallel write System I/O 100,732 126.6 1.3 6.10 CPU time N/A 1,599.3
N/A 10.06
SQL*Net more data to client Network 451,810 103.1 0.2 4.97 db file parallel write System I/O 4,264 784.7 1
84.0 4.93
-direct path write User I/O 121,044 52.5 0.4 2.53 -SQL*Net more data from client Network 7,407,435 279.7
0.0 1.76
-db file parallel write System I/O 986 22.8 23.1 1.10 -SQL*Net more data to client Network 2,714,916 64.6
0.0 0.41
{code}
*To sum it sup:
1. Why is the IO response getting such an hit during the new perf test? Please suggest*
2. Does the number of DB writer impact "log file sync" wait event? We have only one DB writer as the number of cpu on the host is only 4
{code}
select *from v$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - 64bit Production
PL/SQL Release 11.1.0.7.0 - Production
CORE 11.1.0.7.0 Production
TNS for HPUX: Version 11.1.0.7.0 - Production
NLSRTL Version 11.1.0.7.0 - Production
{code}
Please let me know if you would like to see any other stats.
Edited by: Kunwar on May 18, 2013 2:20 PM1. A snapshot interval of 3 hours always generates meaningless results
Below are some details from the 1 hour interval AWR report.
Platform CPUs Cores Sockets Memory(GB)
HP-UX IA (64-bit) 4 4 3 31.95
Snap Id Snap Time Sessions Curs/Sess
Begin Snap: 108129 16-May-13 20:45:32 140 8.0
End Snap: 108133 16-May-13 21:45:53 150 8.8
Elapsed: 60.35 (mins)
DB Time: 140.49 (mins)
Cache Sizes Begin End
~~~~~~~~~~~ ---------- ----------
Buffer Cache: 1,168M 1,168M Std Block Size: 8K
Shared Pool Size: 1,120M 1,120M Log Buffer: 16,640K
Load Profile Per Second Per Transaction Per Exec Per Call
~~~~~~~~~~~~ --------------- --------------- ---------- ----------
DB Time(s): 2.3 0.1 0.03 0.01
DB CPU(s): 0.1 0.0 0.00 0.00
Redo size: 719,553.5 34,374.6
Logical reads: 4,017.4 191.9
Block changes: 1,521.1 72.7
Physical reads: 136.9 6.5
Physical writes: 158.3 7.6
User calls: 167.0 8.0
Parses: 25.8 1.2
Hard parses: 8.9 0.4
W/A MB processed: 406,220.0 19,406.0
Logons: 0.1 0.0
Executes: 88.4 4.2
Rollbacks: 0.0 0.0
Transactions: 20.9
Top 5 Timed Foreground Events
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Avg
wait % DB
Event Waits Time(s) (ms) time Wait Class
log file sync 73,761 6,740 91 80.0 Commit
log buffer space 3,581 541 151 6.4 Configurat
DB CPU 348 4.1
direct path write 238,962 241 1 2.9 User I/O
direct path read temp 487,874 174 0 2.1 User I/O
Background Wait Events DB/Inst: Snaps: 108129-108133
-> ordered by wait time desc, waits desc (idle events last)
-> Only events with Total Wait Time (s) >= .001 are shown
-> %Timeouts: value of 0 indicates value was < .5%. Value of null is truly 0
Avg
%Time Total Wait wait Waits % bg
Event Waits -outs Time (s) (ms) /txn time
log file parallel write 61,049 0 1,891 31 0.8 87.8
db file parallel write 1,590 0 251 158 0.0 11.6
control file parallel writ 1,372 0 56 41 0.0 2.6
log file sequential read 2,473 0 50 20 0.0 2.3
Log archive I/O 2,436 0 20 8 0.0 .9
os thread startup 135 0 8 60 0.0 .4
db file sequential read 668 0 4 6 0.0 .2
db file single write 200 0 2 9 0.0 .1
log file sync 8 0 1 152 0.0 .1
log file single write 20 0 0 21 0.0 .0
control file sequential re 11,218 0 0 0 0.1 .0
buffer busy waits 2 0 0 161 0.0 .0
direct path write 6 0 0 37 0.0 .0
LGWR wait for redo copy 380 0 0 0 0.0 .0
log buffer space 1 0 0 89 0.0 .0
latch: cache buffers lru c 3 0 0 1 0.0 .0 2 The log file sync is a result of commit --> you are committing too often, maybe even every individual record.
Thanks for explanation. +Actually my question is WHY is it so slow (avg wait of 91ms)+3 Your IO subsystem hosting the online redo log files can be a limiting factor.
We don't know anything about your online redo log configuration
Below is my redo log configuration.
GROUP# STATUS TYPE MEMBER IS_
1 ONLINE /oradata/fs01/PERFDB1/redo_1a.log NO
1 ONLINE /oradata/fs02/PERFDB1/redo_1b.log NO
2 ONLINE /oradata/fs01/PERFDB1/redo_2a.log NO
2 ONLINE /oradata/fs02/PERFDB1/redo_2b.log NO
3 ONLINE /oradata/fs01/PERFDB1/redo_3a.log NO
3 ONLINE /oradata/fs02/PERFDB1/redo_3b.log NO
6 rows selected.
04:13:14 perf_monitor@PERFDB1> col FIRST_CHANGE# for 999999999999999999
04:13:26 perf_monitor@PERFDB1> select *from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIME
1 1 40689 524288000 2 YES INACTIVE 13026185905545 18-MAY-13 01:00
2 1 40690 524288000 2 YES INACTIVE 13026185931010 18-MAY-13 03:32
3 1 40691 524288000 2 NO CURRENT 13026185933550 18-MAY-13 04:00Edited by: Kunwar on May 18, 2013 2:46 PM -
45 min long session of log file sync waits between 5000 and 20000 ms
45 min long log file sync waits between 5000 and 20000 ms
Encountering a rather unusual performance issue. Once every 4 hours I am seeing a 45 minute long log file sync wait event being reported using Spotlight on Oracle. For the first 30 minutes the event wait is for approx 5000 ms, followed by an increase to around 20000 ms for the next 15 min before rapidly dropping off and normal operation continues for the next 3 hours and 15 minutes before the cycle repeats itself. The issue appears to maintain it's schedule independently of restarting the database. Statspack reports do not show an increase in commits or executions or any new sql running during the time the issue is occuring. We have two production environments both running identicle applications with similar usage and we do not see the issue on the other system. I am leaning towards this being a hardware issue, but the 4 hour interval regardless of load on the database has me baffled. If it were a disk or controller cache issue one would expect to see the interval change with database load.
I cycle my redo logs and archive them just fine with log file switches every 15-20 minutes. Even during this unusally long and high session of log file sync waits I can see that the redo log files are still switching and are being archived.
The redo logs are on a RAID 10, we have 4 redo logs at 1 GB each.
I've run statspack reports on hourly intervals around this event:
Top 5 Wait Events
~~~~~~~~~~~~~~~~~ Wait % Total
Event Waits Time (cs) Wt Time
log file sync 756,729 2,538,034 88.47
db file sequential read 208,851 153,276 5.34
log file parallel write 636,648 129,981 4.53
enqueue 810 21,423 .75
log file sequential read 65,540 14,480 .50
And here is a sample while not encountering the issue:
Top 5 Wait Events
~~~~~~~~~~~~~~~~~ Wait % Total
Event Waits Time (cs) Wt Time
log file sync 953,037 195,513 53.43
log file parallel write 875,783 83,119 22.72
db file sequential read 221,815 63,944 17.48
log file sequential read 98,310 18,848 5.15
db file scattered read 67,584 2,427 .66
Yes I know I am already tight on I/O for my redo even during normal operations yet, my redo and archiving works just fine for 3 hours and 15 minutes (11 to 15 log file switches). These normal switches result in a log file sync wait of about 5000 ms for about 45 seconds while the 1GB redo log is being written and then archived.
I welcome any and all feedback.
Message was edited by:
acyoung1
Message was edited by:
acyoung1Lee,
log_buffer = 1048576 we use a standard of 1 MB for our buffer cache, we've not altered the setting. It is my understanding that Oracle typically recommends that you not exceed 1MB for the log_buffer, stating that a larger buffer normally does not increase performance.
I would agree that tuning the log_buffer parameter may be a place to consider; however, this issue last for ~45 minutes once every 4 hours regardless of database load. So for 3 hours and 15 minutes during both peak usage and low usage the buffer cache, redo log and archival processes run just fine.
A bit more information from statspack reports:
Here is a sample while the issue is occuring.
Snap Id Snap Time Sessions
Begin Snap: 661 24-Mar-06 12:45:08 87
End Snap: 671 24-Mar-06 13:41:29 87
Elapsed: 56.35 (mins)
Cache Sizes
~~~~~~~~~~~
db_block_buffers: 196608 log_buffer: 1048576
db_block_size: 8192 shared_pool_size: 67108864
Load Profile
~~~~~~~~~~~~ Per Second Per Transaction
Redo size: 615,141.44 2,780.83
Logical reads: 13,241.59 59.86
Block changes: 2,255.51 10.20
Physical reads: 144.56 0.65
Physical writes: 61.56 0.28
User calls: 1,318.50 5.96
Parses: 210.25 0.95
Hard parses: 8.31 0.04
Sorts: 16.97 0.08
Logons: 0.14 0.00
Executes: 574.32 2.60
Transactions: 221.21
% Blocks changed per Read: 17.03 Recursive Call %: 26.09
Rollback per transaction %: 0.03 Rows per Sort: 46.87
Instance Efficiency Percentages (Target 100%)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Buffer Nowait %: 99.99 Redo NoWait %: 100.00
Buffer Hit %: 98.91 In-memory Sort %: 100.00
Library Hit %: 98.89 Soft Parse %: 96.05
Execute to Parse %: 63.39 Latch Hit %: 99.87
Parse CPU to Parse Elapsd %: 90.05 % Non-Parse CPU: 85.05
Shared Pool Statistics Begin End
Memory Usage %: 89.96 92.20
% SQL with executions>1: 76.39 67.76
% Memory for SQL w/exec>1: 72.53 63.71
Top 5 Wait Events
~~~~~~~~~~~~~~~~~ Wait % Total
Event Waits Time (cs) Wt Time
log file sync 756,729 2,538,034 88.47
db file sequential read 208,851 153,276 5.34
log file parallel write 636,648 129,981 4.53
enqueue 810 21,423 .75
log file sequential read 65,540 14,480 .50
And this is a sample during "normal" operation.
Snap Id Snap Time Sessions
Begin Snap: 671 24-Mar-06 13:41:29 88
End Snap: 681 24-Mar-06 14:42:57 88
Elapsed: 61.47 (mins)
Cache Sizes
~~~~~~~~~~~
db_block_buffers: 196608 log_buffer: 1048576
db_block_size: 8192 shared_pool_size: 67108864
Load Profile
~~~~~~~~~~~~ Per Second Per Transaction
Redo size: 716,776.44 2,787.81
Logical reads: 13,154.06 51.16
Block changes: 2,627.16 10.22
Physical reads: 129.47 0.50
Physical writes: 67.97 0.26
User calls: 1,493.74 5.81
Parses: 243.45 0.95
Hard parses: 9.23 0.04
Sorts: 18.27 0.07
Logons: 0.16 0.00
Executes: 664.05 2.58
Transactions: 257.11
% Blocks changed per Read: 19.97 Recursive Call %: 25.87
Rollback per transaction %: 0.02 Rows per Sort: 46.85
Instance Efficiency Percentages (Target 100%)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Buffer Nowait %: 99.99 Redo NoWait %: 100.00
Buffer Hit %: 99.02 In-memory Sort %: 100.00
Library Hit %: 98.95 Soft Parse %: 96.21
Execute to Parse %: 63.34 Latch Hit %: 99.90
Parse CPU to Parse Elapsd %: 96.60 % Non-Parse CPU: 84.06
Shared Pool Statistics Begin End
Memory Usage %: 92.20 88.73
% SQL with executions>1: 67.76 75.40
% Memory for SQL w/exec>1: 63.71 68.28
Top 5 Wait Events
~~~~~~~~~~~~~~~~~ Wait % Total
Event Waits Time (cs) Wt Time
log file sync 953,037 195,513 53.43
log file parallel write 875,783 83,119 22.72
db file sequential read 221,815 63,944 17.48
log file sequential read 98,310 18,848 5.15
db file scattered read 67,584 2,427 .66 -
Hi all, I am using Oracle 10gR2 on Solaris 10.
It did a SQL Trace and came up with the following resultMisses in library cache during parse: 591
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
library cache lock 241 0.06 0.61
KJC: Wait for msg sends to complete 2 0.00 0.00
SQL*Net message to client 1768 0.00 0.00
SQL*Net message from client 1768 0.14 7.94
row cache lock 7 0.00 0.00
gc cr grant 2-way 1 0.00 0.00
db file sequential read 67 0.87 6.73
gc current grant 2-way 19 0.00 0.01
gc current grant busy 58 0.01 0.08
log file sync 3055 0.98 2592.00
gc current block 2-way 14 0.00 0.02
gc cr block 2-way 77 0.00 0.06
log file switch completion 12 0.98 8.80
gc current request 5 1.23 6.15
gc current block lost 1 0.45 0.45
lock deadlock retry 1 0.00 0.00
latch free 1 0.00 0.00
enq: TM - contention 1 0.00 0.00
gc cr request 5 1.23 6.14
gc cr block lost 1 0.31 0.31
cr request retry 1 0.00 0.00
latch: session allocation 1 0.00 0.00
gc buffer busy 2 0.98 1.96
OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
Parse 237 0.08 0.05 0 0 38 0
Execute 2184 0.51 6.17 1 200 585 364
Fetch 1884 0.18 6.96 27 3234 195 2127
total 4305 0.77 13.19 28 3434 818 2491
Misses in library cache during parse: 21
Misses in library cache during execute: 19
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
library cache lock 21 0.00 0.01
row cache lock 248 0.01 0.08
gc cr grant 2-way 3 0.00 0.00
db file sequential read 28 1.01 3.22
gc current grant busy 8 0.00 0.00
gc current block 2-way 5 0.00 0.00
gc cr block 2-way 1 0.00 0.00
log file switch completion 4 0.98 3.55
gc current request 1 1.22 1.22
latch: KCL gc element parent latch 1 0.00 0.00
latch: redo allocation 1 0.00 0.00
gc current block busy 1 0.64 0.64
1181 user SQL statements in session.
314 internal SQL statements in session.
1495 SQL statements in session.There is a lot of log file sync waits. There were a lot of INSERTS in the sql but I did not find any commits. For example
INSERT INTO CM_WORKFLOW_AUDIT (AUDIT_TRAIL_ID, CASE_HISTORY_ID,USER_ID,
GROUP_ID,ACTION_ID,DESCRIPTION,DATE_TIME)
VALUES
('080504001809',2154515,19,2,23,'Ticket[2157817] added to Super Ticket',
TO_DATE('04-05-2008 13:14:38','dd-mm-yyyy HH24:MI:SS'))
But there is no commit at the end, there are a lot of INSERTS like this one but no commit at the end of it. So log file sync cant be waiting to flush the buffer into a redolog (well, that is what I think atleast). Can some one please tell me what is causing the log files sync wait? By the way my log_buffer is 12mb.
Regards.....Hi,
The number of commits can be retrieved from v$sysstat and v$sesstat.
There are no commit statements in any trace file,
you need to look at lines starting with XCTEND in the raw trace data.
Also the size of the log_buffer has 0 to do with the log file sync event, and setting big log_buffer is the typical 'more is better' tuning which doesn't help.
You need to investigate the speed of the devices with holding online redolog, do NOT locate online redologs on RAID-5 devices.
Also posting 'Any one ??' when you are not getting response immediately shows you don't seem to understand this is a volunteer forum.
Sybrand Bakker
Senior Oracle DBA
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