Waits Events and the Geeks who love them Kyle Hailey

Waits Events and the

Geeks who love them

Kyle Hailey

http://perfvision.com

Copyright 2006 Kyle Hailey

#.2

Wait EventsWait EventsWait Events


#.3

And the Geeks Who Love Them


#.4

In this Presentation:

Tuning MethodologyPlan of ActionStatspacks for Collection DataBased on Waits

Waits Cheat Sheet top 36 Waits

Details 4 hardest Waits


#.5

Word of Wisdom

Half of the game is knowing when to act and how much effort to put in


#.6

Database is Hung!

Everybody blames the databasePoor DatabaseYet 9 out of 10 dba’s agree it’s not the

databaseHow do you prove it to management?On the off chance it’s the database, now

we are in some serious trouble!


#.7Database: Guilty until proven innocent

*$%@!!*$%@!!


#.8

Oracle’s Defense

After years of false accusations Oracle took action and created a defense

system:

WAIT EVENTS

To the rescue


#.9

Oracle Instrumentation

RedoRedo Lib Lib CacheCache

Buffer Buffer CacheCache

IOIO

LocksLocks

NetworkNetwork

CPU CPU


#.10

Waits

Instrumented code to indicate bottlenecksNumber of times waitedAmount of time waited

Examples IO LocksSQL*Net

Wouldn’t it be great if Applications took some responsibility and instrumented their code?


#.11

Use Statspack to Find Waits

Statspack Cheat Sheet: Install

Connect as SYSDBA@?/rdbms/admin/spcreate.sql

RunExec statspack.snap;

Generate Reports@?/rdbms/admin/spreport.sql


#.12

Statspack

Look at Top 5 Timed Events (~50 lines down)

Top 5 Timed EventsTop 5 Timed Events~~~~~~~~~~~~~~~~~~ % Total~~~~~~~~~~~~~~~~~~ % TotalEvent Waits Time (s) Call TimeEvent Waits Time (s) Call Time-------------------------------------------- ------------ ----------- ----------------------------------------------------- ------------ ----------- ---------buffer busy waits 2,748 250 78.72buffer busy waits 2,748 250 78.72CPU time 32 10.16CPU time 32 10.16free buffer waits 1,588 15 4.63free buffer waits 1,588 15 4.63write complete waits 10 8 2.51write complete waits 10 8 2.51log buffer space 306 5 1.51log buffer space 306 5 1.51



#.13

Method Relax if

CPU + WAIT << Available CPU

Get to work if

CPU + WAIT >= Available CPU


#.14

Available CPU

Available CPU = # CPUs * Elapsed time

# of CPUs

SQLPLUS> show parameters cpu_count

NAME TYPE VALUE

------------------ -------- ----------

cpu_count integer 2

SQLPLUS> show parameters cpu_count

NAME TYPE VALUE

------------------ -------- ----------

cpu_count integer 2


#.15

Elapsed Time

STATSPACK report for

DB Name DB Id Instance Inst Num Release RAC Host

------- ----------- -------- -------- ---------- --- -------

LABSF03 1420044432 labsf03 1 10.1.0.2.0 NO labsfr

Snap Id Snap Time Sessions Curs/Sess

--------- ------------------ -------- ---------

Begin Snap: 1 03-Apr-06 12:34:06 18 5.6

End Snap: 2 03-Apr-06 12:34:36 18 4.8

Elapsed: 1.00 (mins)



------- ----------- -------- -------- ---------- --- -------



--------- ------------------ -------- ---------

Begin Snap: 1 03-Apr-06 12:34:06 18 5.6

End Snap: 2 03-Apr-06 12:34:36 18 4.8



#.16

Available CPU

# CPUs * Elapsed Time

Example:

2 CPU * ( 1.0 min * (60 sec/min) )

= 120 secs CPU time available

Elapsed: 1.00 (mins) Elapsed: 1.00 (mins)


#.17

Used CPU Time and Wait Time

Look at Top 5 Timed Events




#.18

Example

CPU + WAITS

= 250 + 32 + 15 + 8 + 5 = 310 secs Available CPU was 120 secs 310 >> 120

Get to work tuning ! Event Time (s)Event Time (s)--------------------------- ----------- --------------------------- ----------- buffer busy waits 250 buffer busy waits 250 CPU time 32 CPU time 32 free buffer waits 15 free buffer waits 15 write complete waits 8write complete waits 8log buffer space 5log buffer space 5

Event Time (s)Event Time (s)--------------------------- ----------- --------------------------- ----------- buffer busy waits 250 buffer busy waits 250 CPU time 32 CPU time 32 free buffer waits 15 free buffer waits 15 write complete waits 8write complete waits 8log buffer space 5log buffer space 5


#.19

Dependable Tuning Strategy

Run StatspackTop 5 Timed Events

~50 lines down from top

Need Available CPU Elapsed Time CPU_COUNT

OEM 10gPerformance Page does everything


#.20

Data Sources

StatspackTop 5 Timed Events

10g ASHOEMASH Report : ashrpt.sql

CustomV$session, v$session_wait v$active_session_history


#.21Statspack



------- ----------- -------- -------- ---------- --- -------



--------- ------------------ -------- ---------

Begin Snap: 1 03-Apr-06 12:34:06 18 5.6

End Snap: 2 03-Apr-06 12:34:36 18 4.8




------- ----------- -------- -------- ---------- --- -------



--------- ------------------ -------- ---------

Begin Snap: 1 03-Apr-06 12:34:06 18 5.6

End Snap: 2 03-Apr-06 12:34:36 18 4.8



#.22

Statspack




#.23

OEM 10g

9i &10g Licensed but worth it Does all the work

Aggregates Wait timeSums with CPU timeDisplays available CPUGroups WaitsFilters out unusable waits


#.24

OEM 10g Performance Tab


#.25

OEM 10g Zoom-In

Available CPU

CPU + WAIT


#.26

OEM 10g Zoom-In

Relax Relax Get to Work!Get to Work!


#.27

OEM 10g Zoom-In


#.28

Top Activity Page


#.29

Tuning Methodology

MachineRun queue (CPU)

reduce CPU usage or add CPUs Paging

Reduce memory usage or add memory

Oracle Waits + CPU > Available CPU

Tune waitsCPU 100%

Tune SQL

We are going to We are going to concentrate here concentrate here on WAITSon WAITS


#.30

Waits

360 waits in 9i 36 waits represent 99% of all Bottlenecks

From Anjo Kolks site www.oraperf.comBased on total wait times

12 Wait events represent 80%


#.31Top 12 Waits NAME Count % Total

1. db file sequential read 23,850.00 11.67%2. log file sync 20,594.00 10.08%3. db file scattered read 15,505.00 7.59%4. latch free 11,078.00 5.42%5. enqueue 7,732.00 3.78%6. SQL*Net more data from client 7,510.00 3.67%7. direct path read 5,840.00 2.86%8. direct path write 4,868.00 2.38%9. buffer busy waits 4,589.00 2.25%10. SQL*Net more data to client 3,805.00 1.86% 11. log buffer space 2,990.00 1.46% 12. log file switch completion 2,878.00 1.41%

Above is over 80% of wait times reported

Anjo Kolk www.oraperf.com


#.32Top 36 Waits19. write complete waits 20. library cache lock21. SQL*Net more data from dblink22. log file switch (checkpoint incomplete)23. library cache load lock24. row cache lock25. local write wait26. sort segment request27. process startup28. unread message29. file identify30. pipe put31. switch logfile command32. SQL*Net break/reset to dblink33. log file switch (archiving needed)34. Wait for a undo record35. direct path write (lob)36. undo segment extension

1. db file sequential read2. log file sync3. db file scattered read4. latch free5. enqueue6. SQL*Net more data from client7. direct path read8. direct path write9. buffer busy waits10. SQL*Net more data to client11. log buffer space12. log file switch completion13. library cache pin14. SQL*Net break/reset to client15. io done16. file open17. free buffer waits18. db file parallel read

minus Background, OPS, RAC, PQ, Resource Mgrhttp://www.oraperf.com


#.33

Waits

I/O

Library Cache

Locks

Redo

Buffer Cache

SQL*Net

Wait Areas


#.34

Wait Tree

Waits

IO

Buffer Cache

Library Cache

Lock

Redo

SQL Net

Buffer Busy

Rollback

Free lists

IO ReadCache Latches

Library Cache

Shared Pool

TX Row Lock

TX ITL Lock

HW Lock

Write IO

Read IO

Log Buffer

Log File Sync

Log File


#.35

Redo

REDOREDO


#.36

Redo Wait Solutions

2 log file syncCommit less, put redo logs on faster disks

11 log buffer spaceIncrease log buffer

12 log file switch completionIncrease log file sizes

22 log file switch (checkpoint incomplete)Add log files (or increase log file size)

30 switch logfile commandAvoid switching log files

32 log file switch (archiving needed) ***Archive log running out of space


#.37

Library Cache

REDOREDO Lib Lib CacheCache


#.38

Library Cache

4 latch free – need p1,p2,p3library cacheshared pool

13 library cache pinReduce parsing the same cursor concurrently

20 library cache lockAvoid hard parsing same cursor at same time

23 library cache load lockAvoid hard parsing same cursor at same time

24 row cache lock need p1


#.39

Buffer Cache




#.40

Buffer Cache Details

4 latch free – need p1,p2,p3cache buffers chainscache buffers chains LRU

9 buffer busy waits – need p1,p2,p3 and SQL11 log buffer space

Increase log buffer

17 free buffer waitsIncrease buffer cache size

19 write complete waits Increase buffer cache (or tune DBWR)

25 local write waittruncates / reduce cache size


#.41

IO



IOIO


#.42IO 1 db file sequential read

Tune SQL, speed up disks (5-15ms), increase buffer cache3 db file scattered read

FTS - Tune SQL, add indexes, speed up disks (5-15ms)sorts or PQO - tune IO, sort less

7 direct path readsorts or PQO - tune IO, sort less

8 direct path writedirect path load or temp io, improve disk speed 15 io doneIo done by IO slaves, oracleIxxx could also be an idle wait – sort of worthless

16 file openReduce logons/logoffs or keep log files open

18 db file parallel readTune sql, tune io subsystem, increase buffer cache

26 sort segment requestSMON busy, process rollback problem

28 file identifyKeep log files open, reduce checkpoints

34 direct path write (lob)Improve IO, reduce lob write size


#.43

Locks



IOIO

LocksLocks


#.44

Waits 1-9

5 enqueue – need p1,p2,p3 and SQL

HW

TM

TX 4

TX 6

ST

SQ

TS


#.45

Network



IOIO

LocksLocks

NetworkNetwork


#.46

SQL*Net

6 SQL*Net more data from clientUsually OK, reduce data transferred, possible Network problems

10 SQL*Net more data to clientUsually OK, reduce amount of data transferred, possible Network

tuning needed

14 SQL*Net break/reset to clientCheck for errors in sql statement

21 SQL*Net more data from dblinkReduce data transfer, check net response

31 SQL*Net break/reset to dblinkCheck for errors in sql statement sent


#.47

CPU



IOIO

LocksLocks

NetworkNetwork

100% CPU100% CPU

tune highest SQL tune highest SQL


#.48

CPU

Different from Waits Still a Timed Event High CPU & Low Waits

Tune SQL


#.49Application



IOIO

LocksLocks

NetworkNetwork

??

100% CPU100% CPU

tune highest SQL tune highest SQL


#.50

It’s the Application

If all these areas show no contention , it’s the application


#.51

Waits we will Ignore

Background Idle RAC Resource Manager


#.52

Background & Foreground

Background Processes DBWR LGWR PMON SMON Etc

Foreground Processes SQL*Plus Pro*C SQL*Forms Oracle applications

Only interested in Foreground waits


#.53

REDO Log FilesREDO Log Files Data FilesData Files

DBWRDBWRLGWRLGWR

User2User2

User1User1

User3User3

Log BufferLog Buffer

Buffer CacheBuffer CacheLog Log BufferBuffer


SGASGALibrary Library CacheCache

Background Processes

PMONPMON

SMONSMON


#.54

Background Waits

Filter Out Background Waits

Statspack ASH : SESSION_TYPE='FOREGROUND‘ V$session_wait : type='USER'


#.55

Background Waits

ASH 10gAvoid Background waits in ASH with

V$session_wait joined to v$session

Select …from v$active_session_history where SESSION_TYPE='FOREGROUND'

Select …from v$active_session_history where SESSION_TYPE='FOREGROUND'

select …from v$session s, v$session_wait w where w.sid=s.sid and s.type='USER'

select …from v$session s, v$session_wait w where w.sid=s.sid and s.type='USER'


#.56

Idle Waits

Filter Out 10g

where wait_class != ‘Idle’Create a list

9iCreate a list with

Documentation List created from 10g

Select name from v$event_name where wait_class=‘Idle’;

Select name from v$event_name where wait_class=‘Idle’;


#.57

Parallel Query Waits

Filter Out Parallel Query Wait events are unusable

Save waits are both idle and waits

Parallel Query Waits start with ‘PX’ or ‘KX’PX Deq: Par Recov ReplyPX Deq: Parse Reply


#.58

RAC Waits

You are on your own Check documentation If you are not using RAC then no worries 10g

9i RAC and OPS waits usually contain the word “global”

Select event from v$event_name where wait_class=‘Cluster’;

Select event from v$event_name where wait_class=‘Cluster’;


#.59

Resource Manager Waits

Resource manager throttles userCreates waitObfuscates problems

10g

select name from v$event_name where wait_class='Scheduler';

select name from v$event_name where wait_class='Scheduler';


#.60

Easy Waits vs Difficult Waits

Easy Waits Can take action without further investigation

Difficult Waits, needReal time analysis or historical collections

V$session_wait V$session V$sql


#.61

Easy Waits

1. log buffer space Increase log buffer

2. log file switch completion Increase log file sizes

3. log file switch (checkpoint incomplete) Add log files (or increase log file size)

4. log file switch (archiving needed) Archive log running out of space

5. switch logfile command Avoid switching log files

6. write complete waits Increase buffer cache (or tune DBWR)

7. free buffer waits Increase buffer cache size


#.62

Intermediate

Library Cache locks & Pins Run queries to find lockers

IO Check average read times per file

Should be between 5-20 ms Data in Statspack under “File IO Stats”

Check Cache buffer Hit ratio Check db_cache_advice 9i and higher Data in Statspack under “Buffer Pool Advisory”

Tune High IO SQL Need to follow Advanced Wait steps to find SQL


#.63

Intermediate : Lib Cache Handles

1. library cache lock Avoid hard parsing same cursor at same time

2. library cache pin Reduce parsing the same cursor concurrently

3. library cache load lock Avoid hard parsing same cursor at same time


#.64

Intermediate - IO

1. db file sequential read Tune SQL, speed up disks (5-15ms), increase buffer cache

2. db file parallel read -Tune sql, tune io subsystem, increase buffer cache

3. db file scattered read FTS , Tune SQL, add indexes, speed up disks (5-15ms)

4. direct path write (lob) Improve IO, reduce lob write size

5. direct path read sorts or PQO - tune IO, sort less

6. direct path write direct path load or temp io, improve disk speed


#.65

Library cache pin

select

w.sid,

kglob.KGLNAOBJ

from

x$kglob kglob,

v$session_wait w

where

kglob.KGLHDADR= w.P1RAW and

event like '%library%';

select

w.sid,

kglob.KGLNAOBJ

from

x$kglob kglob,

v$session_wait w

where

kglob.KGLHDADR= w.P1RAW and

event like '%library%';


#.66

Library cache lockFind the waiters and who blocks them

column wevent format a20

column bevent format a20

select

waiter.sid waiter,

waiter.p1raw wlockp1,

waiter.event wevent,

blocker_event.sid blocker,

blocker_event.event bevent

from

x$kglpn p,

gv$session blocker_session,

gv$session_wait waiter,

gv$session_wait blocker_event

where

p.kglpnuse=blocker_session.saddr and

p.kglpnhdl=waiter.p1raw and

(waiter.event like 'library cache lock' ) and

blocker_event.sid=blocker_session.sid

order by

waiter.p1raw,waiter.sid

/

column wevent format a20

column bevent format a20

select

waiter.sid waiter,

waiter.p1raw wlockp1,

waiter.event wevent,

blocker_event.sid blocker,

blocker_event.event bevent

from

x$kglpn p,

gv$session blocker_session,

gv$session_wait waiter,

gv$session_wait blocker_event

where

p.kglpnuse=blocker_session.saddr and

p.kglpnhdl=waiter.p1raw and

(waiter.event like 'library cache lock' ) and

blocker_event.sid=blocker_session.sid

order by

waiter.p1raw,waiter.sid

/


#.67

IO

1. db file sequential read Tune SQL, speed up disks (10-20ms), increase buffer cache

2. db file parallel read Tune sql, tune io subsystem, increase buffer cache

3. db file scattered read FTS , Tune SQL, add indexes, speed up disks (5-15ms)

4. direct path write (lob) Improve IO, reduce lob write size

5. direct path read sorts or PQO - tune IO, sort less

6. direct path write direct path load or temp io, improve disk spee


#.68

IO Solutions If

Db scattered ReadDb file sequential ReadDb file parallel Read

ThenCheck average read times per file

Should be between 5-15 ms Data in Statspack under “File IO Stats”

Check Cache buffer Hit ratio Check db_cache_advice 9i and higher Data in Statspack under “Buffer Pool Advisory”

Tune High IO SQL


#.69

IO Solutions : Ave Read TimeFile IO Stats DB/Inst:labsf03 Snaps: 1-2

->Mx Rd Bkt: Max bucket time for single block read

->ordered by Tablespace, File

Tablespace Filename------------------------ ----------------------------------------------------

Av Mx Av

Av Rd Rd Av Av Buffer BufWt

Reads Reads/s (ms) Bkt Blks/Rd Writes Writes/s Waits (ms)

---------- ---- ------- ----- --- ------- ------------ -------- ---------- --

SYSTEM /u01/app/oracle/oradata/labsf03/system01.dbf

445 15 0.4 16 1.0 1,157 39 2,744 93.3

USERS /u01/app/oracle/oradata/labsf03/users01.dbf

223 7 0.5 ### 1.0 9,725 324 4 100.0

File IO Stats DB/Inst:labsf03 Snaps: 1-2

->Mx Rd Bkt: Max bucket time for single block read

->ordered by Tablespace, File

Tablespace Filename------------------------ ----------------------------------------------------

Av Mx Av

Av Rd Rd Av Av Buffer BufWt

Reads Reads/s (ms) Bkt Blks/Rd Writes Writes/s Waits (ms)

---------- ---- ------- ----- --- ------- ------------ -------- ---------- --

SYSTEM /u01/app/oracle/oradata/labsf03/system01.dbf

445 15 0.4 16 1.0 1,157 39 2,744 93.3

USERS /u01/app/oracle/oradata/labsf03/users01.dbf

223 7 0.5 ### 1.0 9,725 324 4 100.0


#.70IO Solutions : Buffer Pool Advisory

Buffer Pool Advisory Size for Size Buffers for Read EstimatedP Est (M) Factor Estimate Factor Physical Reads--- -------- ------ ------------ ------ --------------D 56 .1 6,986 2.3 58,928D 112 .2 13,972 1.6 42,043D 224 .4 27,944 1.0 25,772D 336 .6 41,916 1.0 25,715D 448 .8 55,888 1.0 25,715D 596 1.0 74,351 1.0 25,715D 728 1.2 90,818 1.0 25,715D 840 1.4 104,790 1.0 25,715D 952 1.6 118,762 1.0 25,715D 1,064 1.8 132,734 1.0 25,715

Buffer Pool Advisory Size for Size Buffers for Read EstimatedP Est (M) Factor Estimate Factor Physical Reads--- -------- ------ ------------ ------ --------------D 56 .1 6,986 2.3 58,928D 112 .2 13,972 1.6 42,043D 224 .4 27,944 1.0 25,772D 336 .6 41,916 1.0 25,715D 448 .8 55,888 1.0 25,715D 596 1.0 74,351 1.0 25,715D 728 1.2 90,818 1.0 25,715D 840 1.4 104,790 1.0 25,715D 952 1.6 118,762 1.0 25,715D 1,064 1.8 132,734 1.0 25,715


#.71

IO Solutions

After CheckingFile IO response timesBuffer Cache Hit Ratio

Then the only choice is to Tune the SQLSee Advanced Wait on how to find SQL


#.72

Advanced1. buffer busy waits

“Buffer wait Statistics” v$waitstats P1 file#, p2 block#, p3 class

2. row cache lock “Dictionary Cache Stats“ v$rowcache P1 – rowcache #

3. latch free “Latch Sleep breakdown” V$latch P1 latch#

4. Enqueue Statspack doesn’t help V$lock P1 lock type and mode


#.73

Advanced Waits Need

Wait ArgumentsP1P2P3

SQL Statements Session IDS


#.74

Gathering More Data - Basic

select

s.sid, /*SESSION */ w.event , /* WAIT */

s.sql_hash_value, /* SQL */

w.p1, w.p2, w.p3 /* P1, P2 , P3 */from

v$session s, v$session_wait w where

w.sid=s.sid /

select

s.sid, /*SESSION */ w.event , /* WAIT */

s.sql_hash_value, /* SQL */

w.p1, w.p2, w.p3 /* P1, P2 , P3 */from

v$session s, v$session_wait w where

w.sid=s.sid /


#.75

Gathering More Data – SQL Text

select w.sid, w.event, w.p1, w.p2, w.p3 ,sql.sql_text

from

v$session_wait w,

v$session s,

v$sql sql

where

s.sid = sw.sid and

sql.address(+) = s.sql_address and s.type='USER‘/

select w.sid, w.event, w.p1, w.p2, w.p3 ,sql.sql_text

from

v$session_wait w,

v$session s,

v$sql sql

where

s.sid = sw.sid and

sql.address(+) = s.sql_address and s.type='USER‘/


#.76

SQL Text

col status for a35

select s.sid, s.sql_hash_value, decode(w.wait_time, 0, w.event , 'CPU') as status, w.p1, w.p2, w.p3 sql_textfrom v$session s, v$session_wait w,

v$sql sqlwhere w.sid=s.sid and s.status='ACTIVE' and s.type='USER' and w.event not in ('jobq slave wait',

'rdbms ipc reply')

and sql.address(+) = s.sql_address ;

col status for a35

select s.sid, s.sql_hash_value, decode(w.wait_time, 0, w.event , 'CPU') as status, w.p1, w.p2, w.p3 sql_textfrom v$session s, v$session_wait w,

v$sql sqlwhere w.sid=s.sid and s.status='ACTIVE' and s.type='USER' and w.event not in ('jobq slave wait',

'rdbms ipc reply')

and sql.address(+) = s.sql_address ;


#.77

Gathering More Data - Filtering I

and and lower(w.event) not in (

'queue monitor wait', 'null event', 'pl/sql lock timer', 'px %', 'sql*net message from client', 'sql*net message from dblink', 'dispatcher timer', 'lock manager wait for remote message', 'pipe get', ‘% timer', 'queue messages', 'rdbms ipc message', 'slave wait', 'virtual circuit status', 'wakeup time manager', 'i/o slave wait', 'jobq slave wait', 'queue monitor wait‘)

and and lower(w.event) not in (

'queue monitor wait', 'null event', 'pl/sql lock timer', 'px %', 'sql*net message from client', 'sql*net message from dblink', 'dispatcher timer', 'lock manager wait for remote message', 'pipe get', ‘% timer', 'queue messages', 'rdbms ipc message', 'slave wait', 'virtual circuit status', 'wakeup time manager', 'i/o slave wait', 'jobq slave wait', 'queue monitor wait‘)


#.78

Gathering More Data – Filtering II

col status for a35

select s.sid, s.sql_hash_value, decode(w.wait_time, 0, w.event , 'CPU') as status, w.p1, w.p2, w.p3from v$session s, v$session_wait w where w.sid=s.sid and s.status='ACTIVE' and s.type='USER' and w.event not in ('jobq slave wait',

'rdbms ipc reply');

col status for a35

select s.sid, s.sql_hash_value, decode(w.wait_time, 0, w.event , 'CPU') as status, w.p1, w.p2, w.p3from v$session s, v$session_wait w where w.sid=s.sid and s.status='ACTIVE' and s.type='USER' and w.event not in ('jobq slave wait',

'rdbms ipc reply');


#.79

Detailed Data Results

SID SQL_HASH STATUS P1 P2 P3

---------- -------------- -------------------------------- ---------- ---------- ----------

234 82347421 CPU 1431502854 39 0

235 3336613934 enq: US - contention 1431502854 44 0





248 3333220954 CPU 1650815232 1 0


260 1272059733 CPU 1431502854 44 0


---------- -------------- -------------------------------- ---------- ---------- ----------

234 82347421 CPU 1431502854 39 0






248 3333220954 CPU 1650815232 1 0


260 1272059733 CPU 1431502854 44 0


#.80

Wait Arguments: P1,P2,P3

Each Wait has a 3 parameters P1,P2,P3 Give detailed information Meaning different for each wait Meaning defined in V$event_name


#.81

Wait Arguments ExampleNAME PARAMETER1 PARAMETER2 PARAMETER3----------------------------------- --------------- --------------- ---------------

latch: cache buffers chains address number triesfree buffer waits file# block# set-id#buffer busy waits file# block# class#latch: redo copy address number trieslog buffer spaceswitch logfile commandlog file sync buffer#db file sequential read file# block# blocksenq: TM - contention name|mode object # table/partitionundo segment extension segment#enq: TX - row lock contention name|mode usn<<16 | slot sequencerow cache lock cache id mode requestlibrary cache pin handle address pin address 100*mode+namesplibrary cache load lock object address lock address 100*mask+namesppipe put handle address record length timeout

Select

name, parameter1, parameter2, parameter3 from v$event_name;

Select

name, parameter1, parameter2, parameter3 from v$event_name;


#.82

Difficult Waits

Multiple causes and solutions

Latches Locks Buffer Busy Row Cache Lock


#.83

Latches

Protect memory for concurrent use “protect lines of code”

Light weight locksBit in memoryAtomic processor callFast and cheapGone if memory is lost

Exclusive Generally Sharing reading has been introduced for some latches


#.84

Finding Latches

“latch free” Covers many latches, find the problem latch by

1. select name from v$latchname where latch# = p1; OR

2. Find highest sleeps in Statspack latch section

In 10g, important latches have a wait event latch: cache buffers chains latch: shared pool

latch: library cache


#.85

Statspack : Latch free

Top 5 Timed Events

~~~~~~~~~~~~~~~~~~ % Total

Event Waits Time (s) Ela Time

-------------------------------- ----------- --------

CPU time 76 62.62

latch free 168,185 41 33.45

wait list latch free 251 5 3.71

library cache pin 2 0 .08

log file parallel write 52 0 .06

Top 5 Timed Events

~~~~~~~~~~~~~~~~~~ % Total

Event Waits Time (s) Ela Time

-------------------------------- ----------- --------

CPU time 76 62.62

latch free 168,185 41 33.45

wait list latch free 251 5 3.71

library cache pin 2 0 .08

log file parallel write 52 0 .06


#.86

Latches : Find Highest Sleeps

Use Statspack (or AWR report)

Latch Sleep breakdown for DB: ORA9

-> ordered by misses des

Latch Name Get Requests Misses SleepsSleeps

------------------- -------------- ----------- ----------------------

shared pool 3,044,462 184,517 19,09819,098

library cache 2,242,805 79,554 15,19815,198

kks stats 263,464 2,842 1,7741,774

row cache object 434,844 955 147147

library cache lock 666,668 734 5454

Latch Sleep breakdown for DB: ORA9

-> ordered by misses des

Latch Name Get Requests Misses SleepsSleeps

------------------- -------------- ----------- ----------------------

shared pool 3,044,462 184,517 19,09819,098

library cache 2,242,805 79,554 15,19815,198

kks stats 263,464 2,842 1,7741,774

row cache object 434,844 955 147147

library cache lock 666,668 734 5454


#.87

Easy Latches Cache Buffers LRU Chain

Too much activity , uses multiple buffer caches and/or increase LRU latches

Shared Pool Too much hard parsing, too small a shared pool

Library Cache Latch Hard Parsing

Use bind variables Uses cursor_sharing=force Increase shared pool size if reloads are high Avoid invalidations

Soft Parsing Hold cursors open Use session_cached_cursors Use cursor_space_for_time


#.88

Advanced Latches

Cache Buffers Chains Hot blocks

Need to find the SQL to solve

Root of Index

Partition

X$dual

Select for update


#.89

Buffer Busy Waits

First need to see p3Read (100,110,120,130 )

IO

In 10g becomes

“read by other session”Write (200,210,220,230, 231 )

Depends on Block type


#.90

Buffer Busy Cases

Undo Header - Not enough rollback segments

Undo Block – hot spot in RBS

Data Block Depends on Object type

Segment Header – add free Lists (with Datablock) Free List – add free lists groups


#.91

Buffer Busy Wait - Object

Table Block w/ DML : Table lacks Free lists Index : has hot block, partition or change SQL

select segment_name,

segment_type

from dba_extents

where file_id = P1

and P2 between

block_id and block_id + blocks – 1;

select segment_name,

segment_type

from dba_extents

where file_id = P1

and P2 between

block_id and block_id + blocks – 1;


#.92

Buffer Busy Waits

Statspack

Buffer wait Statistics for DB: ORA9 Instance: ora9 Snaps: 2 -3

-> ordered by wait time desc, waits desc

Tot Wait Avg

Class Waits Time (s) Time (ms)

------------------ ----------- ---------- ---------

data block 1,490 2 1

undo header 2 0 0

Buffer wait Statistics for DB: ORA9 Instance: ora9 Snaps: 2 -3


Tot Wait Avg

Class Waits Time (s) Time (ms)

------------------ ----------- ---------- ---------

data block 1,490 2 1

undo header 2 0 0


#.93

Buffer Busy Waits Statspack

Buffer wait Statistics DB/Inst: linux3 Snaps: 39-42


Class Waits Wait Time(s) Avg Time (ms)------------------ ------ ------------- -------------undo header 1,159 18 16data block 132 2 12file header block 45 0 2segment header 4 0 10undo block 1 0 0

Buffer wait Statistics DB/Inst: linux3 Snaps: 39-42


Class Waits Wait Time(s) Avg Time (ms)------------------ ------ ------------- -------------undo header 1,159 18 16data block 132 2 12file header block 45 0 2segment header 4 0 10undo block 1 0 0


#.94

Buffer Busy Solutions

IF Buffer Busy Waits highFirst look at v$waitstat

Class Time/Count

SQL> select * from v$waitstat;

CLASS COUNT TIME------------------ ---------- ----------data block 1 1segment header 0 0free list 0 0undo header 0 0undo block 0 0

SQL> select * from v$waitstat;

CLASS COUNT TIME------------------ ---------- ----------data block 1 1segment header 0 0free list 0 0undo header 0 0undo block 0 0


#.95

Row Cache Lock Statspack

^LDictionary Cache Stats for DB: ORA9 Instance: ora9 Snaps: 1 -2->"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 FinalCache Requests Miss Reqs Miss Reqs Usage----------------- --------- ------ ------- ----- -------- ----------dc_object_ids 45 0.0 0 0 958dc_objects 89 0.0 0 0 1,129dc_segments 69 0.0 0 0 807dc_tablespaces 12 0.0 0 0 13dc_usernames 22 0.0 0 0 19dc_sequences 120,003 0.0 0 120,003 5

^LDictionary Cache Stats for DB: ORA9 Instance: ora9 Snaps: 1 -2->"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 FinalCache Requests Miss Reqs Miss Reqs Usage----------------- --------- ------ ------- ----- -------- ----------dc_object_ids 45 0.0 0 0 958dc_objects 89 0.0 0 0 1,129dc_segments 69 0.0 0 0 807dc_tablespaces 12 0.0 0 0 13dc_usernames 22 0.0 0 0 19dc_sequences 120,003 0.0 0 120,003 5


#.96

Row Cache Lock

Need p1 to see the cache type

SQL> select cache#, parameter from v$rowcache;

CACHE# PARAMETER---------- -------------------------------- 1 dc_free_extents 4 dc_used_extents 2 dc_segments 0 dc_tablespaces 5 dc_tablespace_quotas 6 dc_files 7 dc_users 3 dc_rollback_segments 8 dc_objects 17 dc_global_oids 12 dc_constraints

SQL> select cache#, parameter from v$rowcache;

CACHE# PARAMETER---------- -------------------------------- 1 dc_free_extents 4 dc_used_extents 2 dc_segments 0 dc_tablespaces 5 dc_tablespace_quotas 6 dc_files 7 dc_users 3 dc_rollback_segments 8 dc_objects 17 dc_global_oids 12 dc_constraints


#.97

Row Cache Lock

Find Row Cache Find SQL

Example

row cache : sequence

sql : select seq.next_val

problem : sequence had cache of 1

solution: increase sequence cache to 20


#.98

Enqueues aka Locks

“Enqueue” wait – covers all locks pre 10 Protect data against concurrent changes Lock info written into data structures

Block headersData blocksWritten in cache structures

Shareable in compatible modes


#.99

Finding Locks

Statspack no help V$session_wait needs lots of decoding

P1 tells Lock Type and Mode P2,P3 give more data

Usually Need SQL to solve


#.100

Finding Locks

select sid,

event,

chr(bitand(P1,-16777216)/16777215)||

chr(bitand(P1,16711680)/65535) as "Type",

mod(p1,16) as "mode"

from v$session_wait

where event = 'enqueue‘;

select sid,

event,

chr(bitand(P1,-16777216)/16777215)||

chr(bitand(P1,16711680)/65535) as "Type",

mod(p1,16) as "mode"

from v$session_wait

where event = 'enqueue‘;

SID EVENT Ty mode P2 P3

--- ------- -- ---- ------- ----

240 enqueue TX 6 2686995 433

SID EVENT Ty mode P2 P3

--- ------- -- ---- ------- ----

240 enqueue TX 6 2686995 433


#.101

Locks 10g

10g breaks Enqueues out enq: HW - contention Configuration enq: TM - contention Application enq: TX - allocate ITL entry Configuration enq: TX - index contention Concurrency enq: TX - row lock contention Application enq: UL - contention Application


#.102

Locks : TM & TX

select * from v$lock where type in ('TX', 'TM');

SID TY ID1 ID2 LMODE REQUEST CTIME BLOCK--- -- ---------- ---------- ----- ------- ----- -----151 TX 589855 1592 0 6 4049 0135 TM 53737 0 3 0 4058 0151 TM 53737 0 3 0 4049 0135 TX 589855 1592 6 0 4058 1

select * from v$lock where type in ('TX', 'TM');

SID TY ID1 ID2 LMODE REQUEST CTIME BLOCK--- -- ---------- ---------- ----- ------- ----- -----151 TX 589855 1592 0 6 4049 0135 TM 53737 0 3 0 4058 0151 TM 53737 0 3 0 4049 0135 TX 589855 1592 6 0 4058 1


#.103

Utllockt.sql

@?/rdbms/admin/catlock.sql @?/rdbms/admin/utllockt.sql

WAIT_SES LOCK_TYPE MODE_REQ MODE_HELD LOCK_ID1 LOCK_ID2

--------- ----------- --------- --------- -------- --------

13 None

12 Transaction Exclusive Exclusive 65537 14960

WAIT_SES LOCK_TYPE MODE_REQ MODE_HELD LOCK_ID1 LOCK_ID2

--------- ----------- --------- --------- -------- --------

13 None

12 Transaction Exclusive Exclusive 65537 14960


#.104

Summary Waits make Tuning Easy

Check Machine HealthTune WaitsTune CPU

Tune SQL

Use Statspack or OEM 10g Ignore Background, Idle, PQO (Rac, Resmgr) Cheat Sheet on Top 36 Waits Details on the 4 hardest Waits See http://perfvision.com for more info


#.105

10g v$active_session_history

Best source 10g only Data exists since v7

Can simulate v$active_session_history


#.106

Querying ASH

select select event as "TOP 5 Timed Events", event as "TOP 5 Timed Events", cnt as "Count" from (cnt as "Count" from ( select decode(ash.session_state,select decode(ash.session_state, 'ON CPU','CPU',en.name) event ,'ON CPU','CPU',en.name) event , count(decode(ash.session_state,count(decode(ash.session_state, 'ON CPU','CPU',en.name)) cnt'ON CPU','CPU',en.name)) cntfrom from v$active_session_history ash,v$active_session_history ash, v$event_name env$event_name enwhere en.event# (+) = ash.event# where en.event# (+) = ash.event# and and SAMPLE_TIME > sysdate - (5/(24*60)) SAMPLE_TIME > sysdate - (5/(24*60)) group by decode(ash.session_state,'ON CPU','CPU',en.name)group by decode(ash.session_state,'ON CPU','CPU',en.name)order by count(decode(ash.session_state,order by count(decode(ash.session_state, 'ON CPU','CPU',en.name)) desc'ON CPU','CPU',en.name)) desc) where rownum < 6;) where rownum < 6;

select select event as "TOP 5 Timed Events", event as "TOP 5 Timed Events", cnt as "Count" from (cnt as "Count" from ( select decode(ash.session_state,select decode(ash.session_state, 'ON CPU','CPU',en.name) event ,'ON CPU','CPU',en.name) event , count(decode(ash.session_state,count(decode(ash.session_state, 'ON CPU','CPU',en.name)) cnt'ON CPU','CPU',en.name)) cntfrom from v$active_session_history ash,v$active_session_history ash, v$event_name env$event_name enwhere en.event# (+) = ash.event# where en.event# (+) = ash.event# and and SAMPLE_TIME > sysdate - (5/(24*60)) SAMPLE_TIME > sysdate - (5/(24*60)) group by decode(ash.session_state,'ON CPU','CPU',en.name)group by decode(ash.session_state,'ON CPU','CPU',en.name)order by count(decode(ash.session_state,order by count(decode(ash.session_state, 'ON CPU','CPU',en.name)) desc'ON CPU','CPU',en.name)) desc) where rownum < 6;) where rownum < 6;

Top 5 Timed Events CountTop 5 Timed Events Count

------------------------------------ --------------------------------------------- ---------

log file parallel write 8log file parallel write 8CPU 7CPU 7control file parallel write 3control file parallel write 3null event 3null event 3log file sync 2log file sync 2

Top 5 Timed Events CountTop 5 Timed Events Count

------------------------------------ --------------------------------------------- ---------

log file parallel write 8log file parallel write 8CPU 7CPU 7control file parallel write 3control file parallel write 3null event 3null event 3log file sync 2log file sync 2


#.107

Querying ASH for P1,P2,P3

SID EVENT P1 P2 P3SID EVENT P1 P2 P3

--- ----------------------- --- --- ------ ----------------------- --- --- ---

236 db file scattered read 3 35291 16236 db file scattered read 3 35291 16


248 read by other session 1 13646 1248 read by other session 1 13646 1



245 db file sequential read 1 13591 1245 db file sequential read 1 13591 1

SID EVENT P1 P2 P3SID EVENT P1 P2 P3

--- ----------------------- --- --- ------ ----------------------- --- --- ---



248 read by other session 1 13646 1248 read by other session 1 13646 1



245 db file sequential read 1 13591 1245 db file sequential read 1 13591 1

select select

session_id, session_id,

event,event,

p1, p2, p3p1, p2, p3

from v$ashfrom v$ash

select select

session_id, session_id,

event,event,

p1, p2, p3p1, p2, p3

from v$ashfrom v$ash


#.108

ASH Report ASH report @?/rdbms/admin/ashrpt.sql Pick interval over last 7 days !

1) General info

2) Top User Events ***

3) Top Background Events

4) Top Event P1/P2/P3 Values

5) Top Service/Module

6) Top Client IDs

7) Top SQL Command Types

8) Top SQL Statements ***

1) General info

2) Top User Events ***

3) Top Background Events

4) Top Event P1/P2/P3 Values

5) Top Service/Module

6) Top Client IDs

7) Top SQL Command Types

8) Top SQL Statements ***

9) Top SQL using literals

10) Top Sessions ***

11) Top Blocking Sessions

12) Top Sessions running PQs

13) Top DB Objects

14) Top DB Files

15) Top Latches

16) Activity Over Time ***

9) Top SQL using literals

10) Top Sessions ***

11) Top Blocking Sessions

12) Top Sessions running PQs

13) Top DB Objects

14) Top DB Files

15) Top Latches

16) Activity Over Time ***


#.109

V$session_wait

select

decode(w.wait_time, 0, w.event , 'CPU') as "TOP 5 Timed Events”,

count(*) from v$session s,

v$session_wait w

where w.sid=s.sid

and s.status='ACTIVE'

and s.type='USER'

and w.event not in ('jobq slave wait',

'rdbms ipc reply')

group by

decode(w.wait_time, 0, w.event , 'CPU')

order by count(*) desc;

select

decode(w.wait_time, 0, w.event , 'CPU') as "TOP 5 Timed Events”,

count(*) from v$session s,

v$session_wait w

where w.sid=s.sid

and s.status='ACTIVE'

and s.type='USER'

and w.event not in ('jobq slave wait',

'rdbms ipc reply')

group by

decode(w.wait_time, 0, w.event , 'CPU')

order by count(*) desc;

Moment in Time data


#.110

V$session_wait

Top 5 Timed Events Top 5 Timed Events COUNT

----------------------------------- ----------

enq: US – contention 4

CPU 3

buffer busy waits 1

latch: row cache objects 1

Top 5 Timed Events Top 5 Timed Events COUNT

----------------------------------- ----------

enq: US – contention 4

CPU 3

buffer busy waits 1

latch: row cache objects 1


#.111

V$session_wait

col status for a35 select s.sid, s.sql_hash_value, decode(w.wait_time, 0, w.event , 'CPU') as status, w.p1, w.p2, w.p3from v$session s, v$session_wait w where w.sid=s.sid and s.status='ACTIVE' and s.type='USER' and w.event not in ('jobq slave wait', 'rdbms ipc reply');

col status for a35 select s.sid, s.sql_hash_value, decode(w.wait_time, 0, w.event , 'CPU') as status, w.p1, w.p2, w.p3from v$session s, v$session_wait w where w.sid=s.sid and s.status='ACTIVE' and s.type='USER' and w.event not in ('jobq slave wait', 'rdbms ipc reply');


#.112

V$session_wait


---------- -------------- -------------------------------- ---------- ---------- ----------

234 82347421 CPU 1431502854 39 0






248 3333220954 CPU 1650815232 1 0


260 1272059733 CPU 1431502854 44 0


---------- -------------- -------------------------------- ---------- ---------- ----------

234 82347421 CPU 1431502854 39 0






248 3333220954 CPU 1650815232 1 0


260 1272059733 CPU 1431502854 44 0

Moment in Time data


#.113

Waits 1-9

1. db file sequential readTune SQL, speed up disks (5-15ms), increase buffer cache

2. log file syncCommit less, put redo logs on faster disks

3. db file scattered read FTS - Tune SQL, add indexes, speed up disks (5-15ms)

4. latch free – need p1,p2,p3 and sometimes SQL5. enqueue – need p1,p2,p3 and SQL6. SQL*Net more data from client

Usually OK, reduce data transferred, possible Network problems

7. direct path readsorts or PQO - tune IO, sort less

8. direct path writedirect path load or temp io, improve disk speed

9. buffer busy waits – need p1,p2,p3


#.114

Waits 10-18

10. SQL*Net more data to clientUsually OK, reduce amount of data transferred, possible Network tuning needed

11. log buffer spaceIncrease log buffer

12. log file switch completionIncrease log file sizes

13. library cache pinReduce parsing the same cursor concurently

14. SQL*Net break/reset to clientCheck for errors in sql statement

15. io doneIo done by IO slaves, oracleIxxx could also be an idle wait – sort of worthless

16. file openReduce logons/logoffs or keep log files open

17. free buffer waitsIncrease buffer cache size

18. db file parallel readTune sql, tune io subsystem, increase buffer cache


#.115

Waits 19-2719. write complete waits

Increase buffer cache (or tune DBWR)20. library cache lock

Avoid hard parsing same cursor at same time21. SQL*Net more data from dblink

Reduce data transfer, check net response22. log file switch (checkpoint incomplete)

Add log files (or increase log file size)23. library cache load lock

Avoid hard parsing same cursor at same time24. row cache lock

need p1 & SQL25. local write wait

truncates / reduce cache size26. sort segment request

SMON busy, process rollback problem27. process startup

If MTS, increase min servers and dispatchers in init.ora


#.116

Waits 28-36

28. file identifyKeep log files open, reduce checkpoints

29. pipe putSpeed up pipe readers

30. switch logfile commandAvoid switching log files

31. SQL*Net break/reset to dblinkCheck for errors in sql statement sent

32. log file switch (archiving needed)Archive log running out of space

33. Wait for a undo record ??

34. direct path write (lob)Improve IO, reduce lob write size

35. undo segment extensionUse UNDO or with RBS, increase RBS size, avoid OPTIMAL

36. undo segment tx slotUse UNDO, increae # of RBS segs


#.117

Custom Collecting collecting:

ash.collect(sleep,loops)save data in "ash_data" table

sleep = wait time between loops loops = # of loops

Debug or testing:

ash.print(sleep,loops)

prints with dbms_output

to see output, run set serveroutput on execute dbms_output.enable(1000000)


#.118

How much data to keep

create view ash_data_v as

select * from ash_data_1 union all select * from ash_data_2 union all select * from ash_data_3;

create view ash_data_v as

select * from ash_data_1 union all select * from ash_data_2 union all select * from ash_data_3;

internally

max_rows number := 10000;

sets max rows saved in each of 3 tables

in view

ash_data_v


#.119

Sampling ASH Data

Foreground and Background Waiting and CPU Mimics main Fields of ASH


#.120Sampling Select to_char(sysdate,'SSSSS')+ trunc(sysdate-to_date('JAN-01-1970 00:00:00','MON-DD-YYYY HH24:MI:SS'))*86400 , sysdate, s.indx "SID", decode(w.ksusstim, 0,decode(n.kslednam, 'db file sequential read', 'I/O', 'db file scattered read','I/O', 'WAITING'), 'CPU') "STATE", s.ksuseser "SERIAL#", s.ksuudlui "USER#", s.ksusesql "SQL_ADDRESS", s.ksusesqh "SQL_HASH_VALUE" , s.ksuudoct "COMMAND" /* aka SQL_OPCODE */, s.ksuseflg "SESSION_TYPE" , w.ksussopc "EVENT# ", w.ksussseq "SEQ#" /* xksuse.ksuseseq */, w.ksussp1 "P1" /* xksuse.ksusep1 */, w.ksussp2 "P2" /* xksuse.ksusep2 */, w.ksussp3 "P3" /* xksuse.ksusep3 */, w.ksusstim "WAIT_TIME" /* xksuse.ksusetim */, s.ksuseobj "ROW_WAIT_OBJ#", s.ksusefil "ROW_WAIT_FILE#", s.ksuseblk "ROW_WAIT_BLOCK#", s.ksusepnm "PROGRAM", s.ksuseaph "MODULE_HASH", /* ASH collects string */ s.ksuseach "ACTION_HASH" /* ASH collects string */

Select to_char(sysdate,'SSSSS')+ trunc(sysdate-to_date('JAN-01-1970 00:00:00','MON-DD-YYYY HH24:MI:SS'))*86400 , sysdate, s.indx "SID", decode(w.ksusstim, 0,decode(n.kslednam, 'db file sequential read', 'I/O', 'db file scattered read','I/O', 'WAITING'), 'CPU') "STATE", s.ksuseser "SERIAL#", s.ksuudlui "USER#", s.ksusesql "SQL_ADDRESS", s.ksusesqh "SQL_HASH_VALUE" , s.ksuudoct "COMMAND" /* aka SQL_OPCODE */, s.ksuseflg "SESSION_TYPE" , w.ksussopc "EVENT# ", w.ksussseq "SEQ#" /* xksuse.ksuseseq */, w.ksussp1 "P1" /* xksuse.ksusep1 */, w.ksussp2 "P2" /* xksuse.ksusep2 */, w.ksussp3 "P3" /* xksuse.ksusep3 */, w.ksusstim "WAIT_TIME" /* xksuse.ksusetim */, s.ksuseobj "ROW_WAIT_OBJ#", s.ksusefil "ROW_WAIT_FILE#", s.ksuseblk "ROW_WAIT_BLOCK#", s.ksusepnm "PROGRAM", s.ksuseaph "MODULE_HASH", /* ASH collects string */ s.ksuseach "ACTION_HASH" /* ASH collects string */


#.121

Samplingfrom

x$ksuse s , x$ksusecst w, x$ksled n where s.indx != ( select distinct sid from v$mystat ) and bitand(s.ksspaflg,1)!=0 and bitand(s.ksuseflg,1)!=0 and n.indx=w.ksussopc and s.indx = w.indx and ( ( /* status Active - seems inactive & "on cpu"=> not on CPU */ w.ksusstim != 0 and /* on CPU */ bitand(s.ksuseidl,11)=1 /* ACTIVE */ ) or w.ksussopc not in /* waiting and the wait event is not idle */

from

x$ksuse s , x$ksusecst w, x$ksled n where s.indx != ( select distinct sid from v$mystat ) and bitand(s.ksspaflg,1)!=0 and bitand(s.ksuseflg,1)!=0 and n.indx=w.ksussopc and s.indx = w.indx and ( ( /* status Active - seems inactive & "on cpu"=> not on CPU */ w.ksusstim != 0 and /* on CPU */ bitand(s.ksuseidl,11)=1 /* ACTIVE */ ) or w.ksussopc not in /* waiting and the wait event is not idle */


#.122

Sampling Select event# from v$event_name where lower(name) in ( 'queue monitor wait', 'null event', 'pl/sql lock timer', 'px deq: execution msg', 'px deq: table q normal', 'px idle wait', 'sql*net message from client', 'sql*net message from dblink', 'dispatcher timer', 'lock manager wait for remote message', 'pipe get', 'pmon timer', 'queue messages', 'rdbms ipc message', 'slave wait', 'smon timer', 'virtual circuit status', 'wakeup time manager', 'i/o slave wait', 'jobq slave wait', 'queue monitor wait', 'SQL*Net message from client' ) )

Select event# from v$event_name where lower(name) in ( 'queue monitor wait', 'null event', 'pl/sql lock timer', 'px deq: execution msg', 'px deq: table q normal', 'px idle wait', 'sql*net message from client', 'sql*net message from dblink', 'dispatcher timer', 'lock manager wait for remote message', 'pipe get', 'pmon timer', 'queue messages', 'rdbms ipc message', 'slave wait', 'smon timer', 'virtual circuit status', 'wakeup time manager', 'i/o slave wait', 'jobq slave wait', 'queue monitor wait', 'SQL*Net message from client' ) )


#.123

Documents

Waits Events and the Geeks who love them Kyle Hailey