The following listing of the Oracle 10g v$system_event wait events can be used as a reference for any version of Oracle’s wait class. For instance, a db file parallel read wait is considered a User I/O on any version of Oracle. Some versions will not show all of these waits; if the wait does appear, however, its categorization will match this table. It is a useful reference guide when discussing waits with your DBA.
|
EVENT |
WAIT_CLASS# |
WAIT_CLASS |
|
Backup: sbtbackup |
3 |
Administrative |
|
Backup: sbtclose2 |
3 |
Administrative |
|
Backup: sbtend |
3 |
Administrative |
|
Backup: sbterror |
3 |
Administrative |
|
Backup: sbtinfo2 |
3 |
Administrative |
|
Backup: sbtinit |
3 |
Administrative |
|
Backup: sbtinit2 |
3 |
Administrative |
|
Backup: sbtremove2 |
3 |
Administrative |
|
Backup: sbtwrite2 |
3 |
Administrative |
|
buffer busy waits |
4 |
Concurrency |
|
buffer deadlock |
0 |
Other |
|
CGS wait for IPC msg |
0 |
Other |
|
class slave wait |
6 |
Idle |
|
control file heartbeat |
0 |
Other |
|
control file parallel write |
9 |
System I/O |
|
control file sequential read |
9 |
System I/O |
|
control file single write |
9 |
System I/O |
|
cr request retry |
0 |
Other |
|
cursor: mutex S |
4 |
Concurrency |
|
cursor: mutex X |
4 |
Concurrency |
|
cursor: pin S |
0 |
Other |
|
cursor: pin S wait on X |
4 |
Concurrency |
|
Data file init write |
8 |
User I/O |
|
db file parallel read |
8 |
User I/O |
|
db file parallel write |
9 |
System I/O |
|
db file scattered read |
8 |
User I/O |
|
db file sequential read |
8 |
User I/O |
|
db file single write |
8 |
User I/O |
|
DFS lock handle |
0 |
Other |
|
DIAG idle wait |
6 |
Idle |
|
direct path read |
8 |
User I/O |
|
direct path read temp |
8 |
User I/O |
|
direct path write |
8 |
User I/O |
|
direct path write temp |
8 |
User I/O |
|
enq: AF - task serialization |
0 |
Other |
|
enq: AS - service activation |
0 |
Other |
|
enq: BR - file shrink |
0 |
Other |
|
enq: CF - contention |
0 |
Other |
|
enq: CN - race with init |
0 |
Other |
|
enq: CT - state |
0 |
Other |
|
enq: DL - contention |
0 |
Other |
|
enq: DM - contention |
0 |
Other |
|
enq: DR - contention |
0 |
Other |
|
enq: FB - contention |
0 |
Other |
|
enq: FU - contention |
0 |
Other |
|
enq: HW - contention |
2 |
Configuration |
|
enq: IA - contention |
0 |
Other |
|
enq: IR - contention |
0 |
Other |
|
enq: JQ - contention |
0 |
Other |
|
enq: JS - contention |
0 |
Other |
|
enq: JS - job recov lock |
0 |
Other |
|
enq: JS - job run lock - synchronize |
0 |
Other |
|
enq: JS - q mem clnup lck |
0 |
Other |
|
enq: JS - queue lock |
0 |
Other |
|
enq: JS - wdw op |
0 |
Other |
|
enq: KM - contention |
0 |
Other |
|
enq: KO - fast object checkpoint |
1 |
Application |
|
enq: MD - contention |
0 |
Other |
|
enq: MR - contention |
0 |
Other |
|
enq: MW - contention |
0 |
Other |
|
enq: PD - contention |
0 |
Other |
|
enq: PE - contention |
0 |
Other |
|
enq: PI - contention |
0 |
Other |
|
enq: PR - contention |
0 |
Other |
|
enq: PS - contention |
0 |
Other |
|
enq: PW - flush prewarm buffers |
1 |
Application |
|
enq: RO - fast object reuse |
1 |
Application |
|
enq: RS - persist alert level |
0 |
Other |
|
enq: RS - prevent file delete |
0 |
Other |
|
enq: RT - contention |
0 |
Other |
|
enq: SK - contention |
0 |
Other |
|
enq: SQ - contention |
2 |
Configuration |
|
enq: SS - contention |
2 |
Configuration |
|
enq: SW - contention |
0 |
Other |
|
enq: TA - contention |
0 |
Other |
|
enq: TC - contention |
0 |
Other |
|
enq: TC - contention2 |
0 |
Other |
|
enq: TD - KTF dump entries |
0 |
Other |
|
enq: TL - contention |
0 |
Other |
|
enq: TM - contention |
1 |
Application |
|
enq: TO - contention |
0 |
Other |
|
enq: TQ - DDL contention |
0 |
Other |
|
enq: TQ - TM contention |
0 |
Other |
|
enq: TS - contention |
0 |
Other |
|
enq: TT - contention |
0 |
Other |
|
enq: TX - allocate ITL entry |
2 |
Configuration |
|
enq: TX - contention |
0 |
Other |
|
enq: TX - index contention |
4 |
Concurrency |
|
enq: TX - row lock contention |
1 |
Application |
|
enq: US - contention |
0 |
Other |
|
enq: WF - contention |
0 |
Other |
|
enq: WL - contention |
0 |
Other |
|
enq: WP - contention |
0 |
Other |
|
enq: XR - database force logging |
0 |
Other |
|
gc buffer busy |
11 |
Cluster |
|
gc cr block 2-way |
11 |
Cluster |
|
gc cr block busy |
11 |
Cluster |
|
gc cr block congested |
11 |
Cluster |
|
gc cr block lost |
11 |
Cluster |
|
gc cr disk read |
11 |
Cluster |
|
gc cr failure |
11 |
Cluster |
|
gc cr grant 2-way |
11 |
Cluster |
|
gc cr grant congested |
11 |
Cluster |
|
gc cr multi block request |
11 |
Cluster |
|
gc current block 2-way |
11 |
Cluster |
|
gc current block busy |
11 |
Cluster |
|
gc current block lost |
11 |
Cluster |
|
gc current block unknown |
11 |
Cluster |
|
gc current grant 2-way |
11 |
Cluster |
|
gc current grant busy |
11 |
Cluster |
|
gc current grant congested |
11 |
Cluster |
|
gc current multi block request |
11 |
Cluster |
|
gc current retry |
11 |
Cluster |
|
gc current split |
11 |
Cluster |
|
gc domain validation |
11 |
Cluster |
|
gc recovery quiesce |
11 |
Cluster |
|
gc remaster |
11 |
Cluster |
|
gcs drm freeze in enter server mode |
0 |
Other |
|
gcs enter server mode |
0 |
Other |
|
gcs log flush sync |
0 |
Other |
|
gcs remote message |
6 |
Idle |
|
gcs resource directory to be unfrozen |
0 |
Other |
|
ges cgs registration |
0 |
Other |
|
ges enter server mode |
0 |
Other |
|
ges global resource directory to be frozen |
0 |
Other |
|
ges inquiry response |
0 |
Other |
|
ges lmd and pmon to attach |
0 |
Other |
|
ges LMD suspend for testing event |
0 |
Other |
|
ges LMD to inherit communication channels |
0 |
Other |
|
ges lmd/lmses to freeze in rcfg - mrcvr |
0 |
Other |
|
ges lmd/lmses to unfreeze in rcfg - mrcvr |
0 |
Other |
|
ges LMON to get to FTDONE |
0 |
Other |
|
ges reconfiguration to start |
0 |
Other |
|
ges remote message |
6 |
Idle |
|
ges2 LMON to wake up LMD - mrcvr |
0 |
Other |
|
ges2 LMON to wake up lms - mrcvr 2 |
0 |
Other |
|
global enqueue expand wait |
0 |
Other |
|
i/o slave wait |
6 |
Idle |
|
imm op |
0 |
Other |
|
inactive session |
0 |
Other |
|
instance state change |
0 |
Other |
|
io done |
9 |
System I/O |
|
IPC send completion sync |
0 |
Other |
|
jobq slave wait |
6 |
Idle |
|
JS coord start wait |
3 |
Administrative |
|
JS kgl get object wait |
3 |
Administrative |
|
kjbdrmcvtq lmon drm quiesce: ping completion |
0 |
Other |
|
KJC: Wait for msg sends to complete |
0 |
Other |
|
kjctssqmg: quick message send wait |
0 |
Other |
|
kksfbc child completion |
0 |
Other |
|
ksdxexeotherwait |
0 |
Other |
|
ksxr poll remote instances |
0 |
Other |
|
latch free |
0 |
Other |
|
latch: cache buffer handles |
0 |
Other |
|
latch: cache buffers chains |
4 |
Concurrency |
|
latch: cache buffers lru chain |
0 |
Other |
|
latch: checkpoint queue latch |
0 |
Other |
|
latch: enqueue hash chains |
0 |
Other |
|
latch: gcs resource hash |
0 |
Other |
|
latch: ges resource hash list |
0 |
Other |
|
latch: KCL gc element parent latch |
0 |
Other |
|
latch: library cache |
4 |
Concurrency |
|
latch: library cache lock |
4 |
Concurrency |
|
latch: library cache pin |
4 |
Concurrency |
|
latch: messages |
0 |
Other |
|
latch: object queue header operation |
0 |
Other |
|
latch: redo allocation |
0 |
Other |
|
latch: redo writing |
2 |
Configuration |
|
latch: row cache objects |
4 |
Concurrency |
|
latch: session allocation |
0 |
Other |
|
latch: shared pool |
4 |
Concurrency |
|
latch: undo global data |
0 |
Other |
|
LGWR wait for redo copy |
0 |
Other |
|
library cache load lock |
4 |
Concurrency |
|
library cache lock |
4 |
Concurrency |
|
library cache pin |
4 |
Concurrency |
|
local write wait |
8 |
User I/O |
|
lock deadlock retry |
0 |
Other |
|
lock escalate retry |
0 |
Other |
|
Log archive I/O |
9 |
System I/O |
|
log buffer space |
2 |
Configuration |
|
log file parallel write |
9 |
System I/O |
|
log file sequential read |
9 |
System I/O |
|
log file single write |
9 |
System I/O |
|
log file switch (checkpoint incomplete) |
2 |
Configuration |
|
log file switch completion |
2 |
Configuration |
|
log file sync |
5 |
Commit |
|
log switch/archive |
0 |
Other |
|
name-service call wait |
0 |
Other |
|
os thread startup |
4 |
Concurrency |
|
PL/SQL lock timer |
6 |
Idle |
|
pmon timer |
6 |
Idle |
|
PX Deq Credit: need buffer |
6 |
Idle |
|
PX Deq Credit: send blkd |
0 |
Other |
|
PX Deq: Execute Reply |
6 |
Idle |
|
PX Deq: Execution Msg |
6 |
Idle |
|
PX Deq: Join ACK |
6 |
Idle |
|
PX Deq: Msg Fragment |
6 |
Idle |
|
PX Deq: Parse Reply |
6 |
Idle |
|
PX Deq: reap credit |
0 |
Other |
|
PX Deq: Signal ACK |
0 |
Other |
|
PX Idle Wait |
6 |
Idle |
|
PX qref latch |
0 |
Other |
|
rdbms ipc message |
6 |
Idle |
|
rdbms ipc reply |
0 |
Other |
|
read by other session |
8 |
User I/O |
|
reliable message |
0 |
Other |
|
RMAN backup & recovery I/O |
9 |
System I/O |
|
row cache lock |
4 |
Concurrency |
|
single-task message |
6 |
Idle |
|
slave exit |
0 |
Other |
|
smon timer |
6 |
Idle |
|
SQL*Net break/reset to client |
1 |
Application |
|
SQL*Net break/reset to dblink |
1 |
Application |
|
SQL*Net message from client |
6 |
Idle |
|
SQL*Net message from dblink |
6 |
Idle |
|
SQL*Net message to client |
7 |
Network |
|
SQL*Net message to dblink |
7 |
Network |
|
SQL*Net more data from client |
7 |
Network |
|
SQL*Net more data from dblink |
7 |
Network |
|
SQL*Net more data to client |
7 |
Network |
|
SQL*Net more data to dblink |
7 |
Network |
|
Streams AQ: qmn coordinator idle wait |
6 |
Idle |
|
Streams AQ: qmn coordinator waiting for slave to start |
0 |
Other |
|
Streams AQ: qmn slave idle wait |
6 |
Idle |
|
Streams AQ: RAC qmn coordinator idle wait |
6 |
Idle |
|
Streams AQ: waiting for messages in the queue |
6 |
Idle |
|
Streams AQ: waiting for time management or cleanup tasks |
6 |
Idle |
|
switch logfile command |
3 |
Administrative |
|
undo segment extension |
2 |
Configuration |
|
wait for scn ack |
0 |
Other |
|
wait for tmc2 to complete |
0 |
Other |
|
wait list latch free |
0 |
Other |
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