Join Factorization - This item is, by a roundabout route, a follow-up to yesterday’s note on a critical difference in cardinality estimates that appeared if you used the coales...
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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)
The fix for 16921832 is first included in
Interim patches may be available for earlier versions - click here to check.
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.