On 9/28/2016 11:29 AM, Peter Hunkeler wrote:
Job in question is DB2 reorg utlility job which runs some 30 subtasks in
parallel runs for 2 hours. RMF III (60s intervals) shows that the job mostly
has a good workflow (80%+), is heavily using CP (often 80%-90%) and at the same
time is heavily delayed for CP (40%-60%). The job is seen to use up to 230% CP.
Using more subtasks is not always better.
Within DB2 parallel utility processing there are points of
serialization. Running with too many subtasks can actually degrade
thruput due to contention rather than improve it. The contention can
sometimes make RMF *think* there is more CPU delay than there really is
because the subtasks frequently get suspended and resumed due to the
contention.
The only way to reduce the the CPU delay is to reduce the number of
subtasks demanding CPU or to give the system more CPUs to dispatch
subtasks on.
Regards,
Greg
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