ksim generic wait event

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.


Product (Component)Oracle Server (Rdbms)
Range of versions believed to be affectedVersions BELOW 12.2
Versions confirmed as being affected
Platforms affectedGeneric (all / most platforms affected)


The fix for 16921832 is first included in

Interim patches may be available for earlier versions - click here to check.


Related To:


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
  parallel query is used with automatic degree of parallelism
  many sessions are seen to wait for "ksim generic wait event" 
  then this bug may be suspected.
  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.
  Setting parallel_force_local=true can help avoid this issue.

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