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Performance diminishes over time on AIX 7.1 due to Large Segment Aliasing (Doc ID 1467807.1)

Last updated on FEBRUARY 13, 2019

Applies to:

Oracle Database - Enterprise Edition - Version to [Release 10.2 to 11.2]
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
IBM AIX on POWER Systems (64-bit)


Database performance progressively degrades over time until the instance is restarted.
This could manifested by seeing the same SQL, with the same number of buffer gets is gradually  taking more and more CPU time, thereby increasing the overall elapsed time.  

This addition to CPU will show up under sys time and not user time as shown in the vmstat information bleow:



This problem may be seen after migration to AIX 7.1 from lower versions of the OS.
It will usually only be experienced in RDBMS as a result of a code change that helped to  expose the issue.
RDBMS and lower will not be likely to experience the same performance issue


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