Question: What are the Oracle RAC wait events?
Which RAC wait events are the most important to monitor?
Answer: All Oracle RAC wait events begin with
"gc", indicating a global cache RAC wait event. There are several
RAC wait events that are unique to RAC. For full scripts for
monitoring Oracle RAC wait events, see the downloads in the book
Oracle RAC
and Grid. The following specific RAC-related events should be
monitored:
* RAC wait event - global cache open s: A block was
selected.
* RAC wait event - global cache open x: A block
was selected for IUD.
* RAC wait event - global cache null to s: A
block was transferred for SELECT.
* RAC wait event - global cache null to x: A block
was transferred for IUD.
* RAC wait event - global cache cr request: A block
was requested transferred for consistent read purposes.
* RAC wait event - Global Cache Service Utilization
for Logical Reads.
We can also see RAC wait events in an AWR or STATSPACK report:
Avg
Total Wait wait Waits
Event
Waits Timeouts Time (s) (ms)
/txn
--------------------------- ----------- ---------- ----------
------- --------
gc cr block 2-way
49,722 0
77 2
6.6
gc current block 2-way
36,791 0
52 1
4.9
gc buffer busy
1,726 2
29 17 0.2
gc current block busy
275 0
10 37 0.0
gc cr block busy
2,599 0
6 2
0.3
gc cr multi block request
3,096 0
3 1
0.4
gc current grant busy
7,525 0
3 0
1.0
gcs log flush sync
2,674 104
2 1
0.4
gc current grant 2-way
2,530 0
1 1
0.3
