Instance Caging Not Working As Expected On AIX With SMT4 Enabled
(Doc ID 2342987.1)
Last updated on AUGUST 04, 2018
Applies to:Oracle Database - Enterprise Edition - Version 22.214.171.124 and later
IBM AIX on POWER Systems (64-bit)
On IBM AIX and when SMT4 option is enabled, instance caging cannot limit the usage of CPU very well.
There are 12 cores, and each core has 4 threads, so OS claims that there are 48 CPUs in total.
When enabling Instance Caging and set cpu_count to 24, a consumer group should have maximum utilization limited to 50% OS CPU.
However, the exact CPU utilization of that consumer group can be larger than 50%, and sometimes reached to 100%.
SMT4 option is enabled on IBM AIX.
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