Top five wait events

Hi,
may i know wat are the most top five events we often expect in statspack.

On a healthy system, physical read waits should be the biggest waits after the idle waits. However, also consider whether there are direct read waits (signifying full table scans with parallel query) or db file scattered read waits on an operational (OLTP) system that should be doing small indexed accesses.
http://download-west.oracle.com/docs/cd/B19306_01/server.102/b14211/instance_tune.htm#sthref863

Similar Messages

Enq: TX - row lock contention in TOP 5 wait event

DB version:11.1.0.7.0
I am having enq: TX - row lock contention in top 5 wait event.
AWR analyze period - 9-10(pm). During this time only one sql loader is running to insert the data. No other job are running. So there is no chance of other session blocking this session. is there any chance of row lock contention happen by same session.
SQL> SELECT INDEX_NAME,INDEX_TYPE,UNIQUENESS FROM DBA_INDEXES WHERE TABLE_NAME='DATA_DATA';
INDEX_NAME INDEX_TYPE UNIQUENES
CIDX BITMAP NONUNIQUE
VIDX BITMAP NONUNIQUE
Thanks.

SQL> SELECT INDEX_NAME,INDEX_TYPE,UNIQUENESS FROM DBA_INDEXES WHERE TABLE_NAME='DATA_DATA';
INDEX_NAME INDEX_TYPE UNIQUENES
CIDX BITMAP NONUNIQUE
VIDX BITMAP NONUNIQUEYou have bitmap indexes here on a table being inserted into. Bitmap Indexes are another source of lock(and deadlock) in OLTP application. You said that the SQLloader was the unique active program but may be you are also triggering another procedure after the load. Procedure in which you might be using also automomous transactions and so on...
Check first if your table is subject to DML operation in a a multi-user concurrent accesss and in which case you have to get rid of those bitmap indexes
http://hourim.wordpress.com/2011/03/14/deadlock-%e2%80%93-part-1-bitmap-index/
Best regards
Mohamed Houri
www.hourim.wordpress.com

Interpret DB CPUwait event (top 5 wait event AWR)

Hi,
Can anyone tell me how to read the table below especially the "DB CPU" section,
Is it right to say that 41.71% of time was consumed waiting for CPU?? this is urgent
Event                     Waits           Time(s)      Avg wait (ms)      % DB time      Wait Class
db file sequential read      300,835      1,483           5           58.42           User I/O
DB CPU                     1,059                     41.71
reliable message           9,499           18           2           0.71           Other
PX Deq: Slave Session Stats      6,506           11           2           0.43           Other
gc cr grant 2-way           26,218           6           0           0.25           Cluster

user589420 wrote:
Hi,
Can anyone tell me how to read the table below especially the "DB CPU" section,
Is it right to say that 41.71% of time was consumed waiting for CPU?? this is urgent
Event                           Waits Time(s) Avg wait (ms) % DB time Wait Class
db file sequential read       300,835    1,483              5      58.42 User I/O
DB CPU                                   1,059                     41.71
reliable message                9,499       18              2       0.71 Other
PX Deq: Slave Session Stats     6,506       11              2       0.43 Other
gc cr grant 2-way              26,218        6              0       0.25 Cluster
When posting information to the forum that includes critical spaces, like the above, use a { code } tag (without spaces) before and after the information.
I do not understand why this question is an urgent problem.
It is incorrect to state that 41.71% of the time was consumed waiting for the CPU. When an Oracle process is running on the CPU, it is officially not waiting. It causes a bit of confusion having the CPU time consumed listed among the top 5 wait events, but as long as you understand why it is in the top 5 list, it almost makes sense for it to be included.
The DB CPU statistic is listed as 1,059 seconds. If the duration of this report is 1 hour, that is 3,600 seconds of total time. If there is a single CPU in the server, there are 3,600 CPU seconds available in the time period, indicating that the server's CPU on average was 29.4% busy. If there were 12 CPUs in the server, there were 43,200 CPU seconds available in the time period, indicating that on average the CPUs were 2.5% busy. Does this mean that there was a problem, or was this OK, or is there not enough information? Just because on average the CPUs are not busy, that does not mean that there were not periods of intense CPU competion, where in fact there was a temporary shortage of available CPU time for processing.
The DB Time statistic is supposed to be an indication of work performed by the instance on behalf of the user sessions. It is the accumulation of CPU time consumed by foreground sessions plus the accumulated sum of all non-idle wait events consumed by foreground sessions. Blog articles that might be of interest to you:
http://hoopercharles.wordpress.com/2010/01/13/working-with-oracle-time-model-data/
http://hoopercharles.wordpress.com/2010/02/05/faulty-quotes-6-cpu-utilization/
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.

Imm op in Top 5 wait event

Hi,
I found the event: "imm op" in the top of the "top 5 wait event" , at the awr report (10204 version) .
Is it an idel event ? is related to the fact that the database is bening backedup at the same time (event Backup: sbtbackup ) ?
Is there somthing i can do to reduce it value ?
Thanks
Top 5 Timed Events                                         Avg %Total
~~~~~~~~~~~~~~~~~~                                        wait   Call
Event                                 Waits    Time (s)   (ms)   Time Wait Class
imm op                                5,936       5,879    990   68.8      Other
Backup: sbtbackup                         8       5,752 ######   67.3 Administra
db file scattered read              200,642       3,335     17   39.0   User I/O
CPU time                                          3,177          37.2
log file parallel write             150,271       1,822     12   21.3 System I/O
          -------------------------------------------------------------

Hi Werner,
BACKUP_TAPE_IO_SLAVES is set to TRUE in the case of a RMAN backup if dedicated I/O slave processes are to copy backup write processes to tape and not the Oracle shadow processes. In this case, "imm op" waits only affect the backup runtime, but not the live system.My init.ora parameter are as followed:
backup_tape_io_slaves TRUE
dbwr_io_slaves 0
db_writer_processes 1
I dont know the reason why backup_tape_io_slaves is set to TRUE.
Would you suggest me to set it to FALSE and test it again ?
Thanks
End value
Parameter Name                Begin value                       (if different)
aq_tm_processes               0
background_dump_dest          C:\ORACLE\ADMIN\XXX\BDUMP
backup_tape_io_slaves         TRUE
compatible                    10.2.0
control_files                 D:\ORADATA\XXX\CONTROL01.CTL, D:
core_dump_dest                C:\ORACLE\ADMIN\XXX\CDUMP
db_block_size                 8192
db_cache_size                 8388608
db_domain
db_file_multiblock_read_count 16
db_name                       xxxx
db_recovery_file_dest         T:\oradata\XXX\archive
db_recovery_file_dest_size    1073741824
dispatchers                   (PROTOCOL=TCP) (SERVICE=XXXXDB)
fast_start_mttr_target        300
instance_name                 xxxx
java_pool_size                0
job_queue_processes           3
large_pool_size               0
local_listener                LISTENER_xxxx
log_archive_dest_1            LOCATION=T:\oradata\XXX\archive
log_archive_format            %t_%r_%s.dbf
max_dump_file_size            UNLIMITED
nls_length_semantics          BYTE
open_cursors                  1200
processes                     150
query_rewrite_enabled         FALSE
remote_login_passwordfile     EXCLUSIVE
resource_limit                TRUE
resource_manager_plan
session_cached_cursors        300
session_max_open_files        20
sga_target                    838860800
shared_pool_size              0
sort_area_size                524288
star_transformation_enabled   FALSE
streams_pool_size             50331648
timed_statistics              TRUE
undo_management               AUTO
undo_retention                3600
undo_tablespace               UNDOTBS1
user_dump_dest                C:\ORACLE\ADMIN\XXX\UDUMP
          -------------------------------------------------------------

Top 5 wait events in AWR Repprt

Hi,
The following is top 5 wait event in my AWR reports...
Whenever I take reports this are always top 5 events
Top 5 Timed Events
=============================================================================================================
Event
CPU time
Waits               4,717
% Total Call Time     62.0
log file sync
Waits                64,963
Time(s)               1,362
Avg Wait(ms)          21
% Total Call Time     17.9
Wait Class          Commit
log file parallel write
Waits               63,485
Time(s)               1,004
Avg Wait(ms)          16
% Total Call Time     13.2
Wait Class          System I/O
enq: TX - row lock contention
Waits               348
Time(s)               984
Avg Wait(ms)          2,828
% Total Call Time     12.9
Wait Class          Application
db file parallel write
Waits               29,305
Time(s)               561
Avg Wait(ms)          19
% Total Call Time     7.4
Wait Class          System I/O
------------------------------------------------------------------------------------------------------------

Start with Performance Tuning Guide
10.2.3 Table of Wait Events and Potential Causes

Latches in top 5 wait events

Hi,
I have Oracle 8.1.7.4 running on solaris 8. Recently I bounced the DB and after restart the performance is very slow.
Most of the dictionary related queries take very long.
Top 3 wait events in statspack report are as below:
Top 3 Wait Events
~~~~~~~~~~~~~~~~~ Wait % Total
Event Waits Time (cs) Wt Time
latch free 58,325,603 128,928,423 81.29
sort segment request 200,342 20,671,460 13.03
enqueue 20,465 6,145,889 3.88
Can anyone provide me with some thoughts on it.
Thanks
Ramanbir

Optimizer is still the same CHOOSE and no stats were gathered on sys schema.
However i can see following in v$latch.
SELECT NAME, GETS, SLEEPS, round(SLEEPS*100/SUM(SLEEPS) OVER(),2) SLEEP_PCT, round(SLEEPS*100/GETS,2) SLEEP_RATE
               FROM V$LATCH WHERE GETS>0 ORDER BY SLEEPS DESC;
NAME     GETS     SLEEPS     SLEEP_PCT     SLEEP_RATE
cache buffers chains     161393126526     113344597     62.66     0.07
cache buffer handles     617499052     67425052     37.27     10.92
SGA is as below
Total System Global Area 1906311328 bytes
Fixed Size 73888 bytes
Variable Size 273317888 bytes
Database Buffers 1631854592 bytes
Redo Buffers 1064960 bytes
Raman

Can you please tell me how to find top 10 wait events

Hi
Can you please tell me how to find top 10 wait events and what actions need to be taken when there is a wait?
Thanks
Regards,
RJ.

hi,
suggest you to use statspack !!!!!!! for the all tuning..else use the views
* v$session_event
* v$session_wait
* v$system_event
go through this for tuning tips
http://www.dba-oracle.com/art_dbazine_waits.htm
Thanks
--Raman

Awr report showing "Undo segment recovery" in top 1st wait event.

Hi all.
Today evening oracle.exe is hitting 100% cpu in windows server 2003.
In the awr report "undo segment recovery" listed in the top 5 wait event (1st place) and
also in the enterprise manager it shows the details like,
ACTION 1:
Action Investigate the cause for high "undo segment recovery" waits. Refer to Oracle's "Database Reference" for the description of this wait event. Use given SQL for further investigation.
Rationale The SQL statement with SQL_ID "0x63ctfjb1m1j" was found waiting for "undo segment recovery" wait event.
SQL Text UPDATE PF_SubjectVEChapterPage SET NeedsRecalcState = NULL, NeedsUnsignState = ...
SQL ID 0x63ctfjb1m1j
Rationale The SQL statement with SQL_ID "0x6uvufcw5umh" was found waiting for "undo segment recovery" wait event.
SQL Text
SQL ID 0x6uvufcw5umh
Rationale The SQL statement with SQL_ID "2dvmt5mhr3m10" was found waiting for "undo segment recovery" wait event.
SQL Text UPDATE PF_SubjectVEChapterPage SET NeedsRecalcState = NULL, NeedsUnsignState = ...
SQL ID 2dvmt5mhr3m10
Rationale The SQL statement with SQL_ID "gx5pummu20jzb" was found waiting for "undo segment recovery" wait event.
SQL Text UPDATE PF_SubjectVEChapterPage SET NeedsRecalcState = NULL, NeedsUnsignState = ...
SQL ID gx5pummu20jzb
Rationale The SQL statement with SQL_ID "1rxk3vt41zg1u" was found waiting for "undo segment recovery" wait event.
SQL Text
SQL ID 1rxk3vt41zg1u
ACTION 2:
Investigate the cause for high "undo segment recovery" waits in Module "dllhost.exe".
ACTION 3:
Investigate the cause for high "undo segment recovery" waits in Service "SYS$USERS".
I'm not sure what action i need to take exactly.Please provide your valuable suggestions to proceed further.
Thanks, Muhammed Thameem.

http://download.oracle.com/docs/cd/A97630_01/server.920/a96536/apa5.htm
"undo segment recovery
PMON is rolling back a dead transaction. The wait continues until rollback finishes.
Wait Time: 3 seconds
Parameters:
segment# -> The ID of the rollback segment that contains the transaction that is being rolled back
tx flags -> The transaction flags (options) set for the transaction that is being rolled back?

( name-service call wait   ) event   is amoung the top 5 wait events

10.2.0.3 2node- RAC
When I check the wait event in the active session wait event the sessions can be see that they are blocked by the LMON process. The wait event appears only on one node.
It is very hard to find information on the net or on the metalink.
How could I overcome this wait event ?
select program, type from v$session
     where sid in
     (select blocking_session from v$active_session_history
               where event like 'name-service%'
     and rownum < 1000 )
oracle@dbokyanus1 (LMON) , BACKGROUND
Top 5 Timed Events Avg %Total
~~~~~~~~~~~~~~~~~~ wait Call
Event Waits Time (s) (ms) Time
db file sequential read 4,331,507 15,218 *4* *31.2*
CPU time *8* *17.5*
log file sync 1,462,968 5,513 *4* *11.3*
name-service call wait 72,058 4,545 *63* *9.3*
SQL*Net message from dblink 4,197 4,047 *964* *8.3*

oceanic-815 wrote:
10.2.0.3 2node- RAC
When I check the wait event in the active session wait event the sessions can be see that they are blocked by the LMON process. The wait event appears only on one node.
It is very hard to find information on the net or on the metalink.
If I use Google to find information about this
I ran into this page.
There is indeed not much to find about this wait-event, other than there is probably some sort of network communication problem between the two nodes.
Maybe the best solution is to raise a S/R at Oracle support

Latch: session allocation in top 5 wait events

Hi,
This wait event session is coming in the top 5 timed events
How to proceed for solving this issue?
This database is only being used for migration activities currently,which means a lot of imports going on.
PFB the Top 5 Timed Foreground Events
++++++++++++++++++
Event     Waits     Time(s)     Avg wait (ms)     % DB time     Wait Class
DB CPU          8,437          57.95
latch: session allocation     2,035,326     3,671     2     25.22     Other
wait list latch free     243,511     2,448     10     16.81     Other
direct path write     504,262     363     1     2.49     User I/O
log file sync     39,396     156     4     1.07     Commit
++++++++++++++++++
Cheers,
Kunwar

user9131570 wrote:
This database is only being used for migration activities currently,which means a lot of imports going on.
PFB the Top 5 Timed Foreground Events
++++++++++++++++++
Event     Waits     Time(s)     Avg wait (ms)     % DB time     Wait Class
DB CPU          8,437          57.95
latch: session allocation     2,035,326     3,671     2     25.22     Other
wait list latch free     243,511     2,448     10     16.81     Other
direct path write     504,262     363     1     2.49     User I/O
log file sync     39,396     156     4     1.07     Commit
++++++++++++++++++
A little more information would help - you could start with the Load Profile section, and the summary of the number of sessions, CPU, and memory. Also OSSTATs might be helpful and the Time Model stats. The version of Oracle might also be relevant.
See the note below about using the "code" tag and preview option.
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.
There is a +"Preview"+ tab at the top of the text entry panel. Use this to check what your message will look like before you post the message. If it looks a complete mess you're unlikely to get a response. (Click on the +"Plain text"+ tab if you want to edit the text to tidy it up.)
+"Science is more than a body of knowledge; it is a way of thinking"+
+Carl Sagan+

Top 5 wait event

I need some guidance on my AWR 5 top wait events
I have 10gR2 on Solaris 9.
The top 5 events in my AWR (ran hourly) always contain the following: (not necessary in order)
CPU time
control file parallel write
dbfile parallel write
log file parallel write
log file sync.
Is this an indication of an undersized log buffer ?
My value for log buffer is 14,258,176
I have 4 CPUs
I'd appreciate any help

Hi!
I do have the same problem and trying to figure it out
Top 5 Timed Events Avg %Total
~~~~~~~~~~~~~~~~~~ wait Call
Event Waits Time (s) (ms) Time Wait Class
CPU time 932 71.3
reliable message 2,828 509 180 38.9 Other
control file parallel write 8,759 300 34 23.0 System I/O
db file parallel write 19,813 238 12 18.2 System I/O
control file sequential read 65,435 193 3 14.7 System I/O
share with me, your thoughts
Ravi

Flashback buf free by RVWR is in top-5 wait event.

Hi Team,
I am having slowness in my database. due to this i am getting some of the query getting timed out. while i view the AWR ,i am seeing the wait event-flashback buf free by RVWR. Can you please help me will it affect the database performance. and in the foreground wait even.
flashback buf free by RVWR shows :132waits & 90 timout. ( what is the meaning of timout) is that meaning 90 timeout to wait for flashback file system.
Event Waits Time(s) Avg wait (ms) % DB time Wait Class
control file sequential read 3,013 3,836 1273 53.25 System I/O
db file sequential read 298,849 1,522 5 21.13 User I/O
unspecified wait event 299,096 728 2 10.10 Other
DB CPU 682 9.47
flashback buf free by RVWR 132 125 945 1.73 Other
Please help me on this.
Thanks.

Format your thread please using

How to resolve wait event

according to statspack report top five waits events are:-
Event Waits Time (s) Ela Time
db file sequential read 15,496 651 55.53
CPU time 470 40.09
control file parallel write 643 15 1.26
log file sync 518 13 1.14
db file parallel write 252 10 .85
But how can i resolve these events.Please help me. I am not well aware about tuning aspect.
Thanks in advance

You input is very restricted, no one can't really advice on this. You would have given more info.
As you can see, 'db file sequential read' is the top most wait event. Which mean, you are using wrong index or index doesn't required. Look at the top sqls in the stats pack nd tune them.
This also due to the fact the your index statsitics are not providing enough good info to optimizer.
Jaffar

Top five events

Hi,
may i know wat are the most top five events we often expect in statspack.
With Regards
Boo

top five wait events
C.

Top Wait Events Query is needed

Hi,
I hope I'm asking this question in right place.
I need a script and its output should give me the top 5 wait events in last 1 hour for an instance.

986330 wrote:
Hi,
I hope I'm asking this question in right place.
I need a script and its output should give me the top 5 wait events in last 1 hour for an instance.
which Top 5? Top number of Waits? Top Total time Waited? Top Avg Wait Time?
why don't you just run AWR report?

Top five wait events

Similar Messages

Maybe you are looking for