My Oracle Support Banner

Instance Caging Not Working As Expected On AIX With SMT4 Enabled (Doc ID 2342987.1)

Last updated on JANUARY 15, 2020

Applies to:

Oracle Database - Enterprise Edition - Version 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
Oracle Database Cloud Exadata Service - Version N/A 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.

For example,

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.


To view full details, sign in with your My Oracle Support account.

Don't have a My Oracle Support account? Click to get started!

In this Document

My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts.