Problem

After a system update to an AIX 6.1 machine an Enterprise Server IMS DB based application suffered from a severe performance degradation. The symptom was particularly high CPU usage on the casdbc64 process.

Solution

This issue was found to be introduced by specifying an olson format eg:-

TZ=Europe/Rome

On AIX this use of olsen timezones can have a performance penalty over posix format timezones.

IBM document this issue here:-

https://www-304.ibm.com/support/docview.wss?uid=isg1IZ86764

and in the AIX documentation for the TZ environment variable at:-

http://pic.dhe.ibm.com/infocenter/aix/v7r1/index.jsp?topic=/com.ibm.aix.prftungd/doc/prftungd/misc_tun_params.htm

Switching to a posix format timezone resolved the problem.