DB2 on P7 system, System CPU may spike.

If there is many CPUs (over the CPUs or even to + CPUs) on AIX platform, there might is a performance problem (very high C PU) caused by bad performance of Thread_unlock during very high DB2 latch contention.

The main symptom at DB2 side is sqlospinlockreleaseconflict would cost a long time (over microseconds) to release a LATC H and many latch-waiters is waiting on this latch.

The root cause is an AIX kernel call Thread_unlock (called by DB2 function Sqlospinlockreleaseconflict) does not provide good Performance in extreme high workload. The solution is applying AIX fix and DB2 fix together.


Below is the AIX APAR information.

6.1 TL06 SP7 (IV10411)
6.1 TL07 SP2 (IV10010)
6.1 TL08 (IV13362)
7.1 GA SP5 (IV14638)
7.1 TL01 SP2 (IV09962)


Below is the corresponding DB2 APAR information.

DB2 v97 APAR is IC79285, which are expected to being fixed in V97FP6. This APAR would provide fix to implement AIX new API thread_unlock_extended (). After installing DB2 fix, to do use of the new AIX API thread_unlock_extended, a new DB2 registry variable is needed to be t Urned on.

Db2set Db2_enable_thread_unlock_extended=yes
Db2start

DB2 on P7 system, System CPU may spike.