"resmgr:cpu quantum" waits appearing and the performance is slow

The above symptom is noticed on 11.1.0.6 database. We came across this issue on one of our databases which was running slow when the backups were kicking in. Our database was not having any Resource Consumer Plans. However, from 11g onwards, every maintenance window is part of a DEFAULT resource plan by default. As soon as the maintenance windows open, the DEFAULT plan gets associated with it. The issue we had was that our backup window was falling in the maintenance window.

As a workaround to this issue, we disabled the resource plans from the maintenance windows and the wait disappeared.

However, I do recommend that the database running on 11.1.0.6 patchset should be patched to 11.1.0.7 to overcome this issue. And also, Oracle has associated the Maintenance Windows with the DEFAULT resource plans for a reason so we should stick with that which we can do on 11.1.0.7 patchset or higher.


As per MOSS note 6874858.8, the description and workaround is as follows:

When RMAN is running with Resource Manager enabled, the performance of
the system may degrade. Users may have problems logging in.
When this occurs large waits will be seen with the wait event
"resmgr:cpu quantum" with low CPU utilization.

Workaround
Disable Resource Manager.