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High CPU by Sessions Holding DX Enqueue; Others Waiting 'enq: DX - contention' (Doc ID 1275884.1)

Last updated on JULY 14, 2020

Applies to:

Oracle Database - Enterprise Edition - Version to [Release 10.2 to 11.1]
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Information in this document applies to any platform.


High CPU is observed  by sessions attempting to end / abort a distributed transaction.

These sessions are holding a DX enqueue.

The DX enqueue is associated with distributed transaction activity.

Other sessions waiting on the above may exhibit higher than usual waits on related events:
- 'enq: DX - contention' ,      or
- 'inactive transaction branch'

A system state dump which can be generated using using the detail in <Note:125568.1> shows that
those processes which are using CPU have a short stack which is similar to the following; please generate 3 system states 2 minutes apart  :

... <-kssdct()+106<-kqldaso()+66<-ktcrab()+207<-ktdabt()+471<-k2labo()+203<-k2send() ...

k2send() indicates the processing of a 2 phase commit operation;
k2labo() indicates an abort() operation;
kssdct()  is connected with deleting a state object .
This operation should be short lived and therefore should not appear in successive systemstates.


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