In Oracle performance monitoring why does Scheduler activity goes up

Question

What does scheduler mean in Oracle? Is it connection scheduling or query scheduling or the query plan execution scheduling or something else?

Answer 1

In this case I suspect you mean the scheduler than runs jobs at certain times. (It used to be called/accessed via DBMS_JOB if that rings any bells?)

I would guess that the Performance Monitor schedules regular jobs to look at query statistics etc, hence the increase in activity.

Answer 2

In 10g and above, the term "scheduler" usually refers to the processes that are running under the new Oracle job scheduler that was introduced in that release. Prior to 10g, there was a less functional scheduler and jobs that were running under that were usually referred to as "dbms jobs" because the API used to manage them was the PL/SQL built-in package DBMS_JOB.

Other info:

• Both types of scheduled jobs exist as of the 11g release - the API for the new jobs is DBMS_SCHEDULER
• DBMS_SCHEDULER adds several important enhancements such as the ability to run targets other than PL/SQL blocks, logging, interfaces to maintenance windows, and friendlier specification of the time intervals between executions
• A standard install of Enterprise Edition will create several DBMS_SCHEDULER jobs out of the box - probably the only one you'll ever need to modify/replace/reschedule is the job that computes statistics for the optimizer.

Answer 3

It could very well be that normal queries are controlled by resource manager. In that case you see waits for scheduler in grid control, without having run a single scheduled job.

best regards, Ronald