Bug 16921832 Very high "ksim generic wait event" from parallel query in a RAC environment
This note gives a brief overview of bug 16921832. The content was last updated on: 08-FEB-2015 Click here for details of each of the sections below.
Affects:
Product (Component) | Oracle Server (Rdbms) |
Range of versions believed to be affected | Versions BELOW 12.2 |
Versions confirmed as being affected |
|
Platforms affected | Generic (all / most platforms affected) |
Fixed:
The fix for 16921832 is first included in |
|
Interim patches may be available for earlier versions - click here to check.
Description
This bug is only relevant when using Real Application Clusters (RAC) and Parallel Query (PQO)
Very high "ksim generic wait event" may be seen when using parallel query in a RAC
environment with auto DOP. Also OCSSD may use high CPU.
Rediscovery Notes
If the system is RAC
AND
parallel query is used with automatic degree of parallelism
AND
many sessions are seen to wait for "ksim generic wait event"
then this bug may be suspected.
AND
OCSSD keeps reporting 'clssgmGroupState: requested group state of unknown group'
If an interim patch for 16554552 has been installed then an ORA-7445 [kjuinc]
might be seen with kxfpRefreshInst on the stack. This fix should be used in place of that fix.
Workaround
Setting parallel_force_local=true can help avoid this issue.