RAC Cluster Waits

Hi,

I have a 10.2 RAC with 3 nodes. It is an OLTP system.

We are seeing what may be "excessive" cluster waits.

I need to know how to judge what is ACTUALLY excessive, and how to tune the system. Please direct me to a detailed or complete refrence describing the parts of "Cluster" and how to tune them. I see many lists of wait events on the web, but no description nor how to tune.

Why do I think it may be excessive?

This was a CPU intensive system in the 9i, non-RAC environment, I expected the CPU to be a sizable percentage of waits/activity.

Our system runs fine except during our bi-weekly crunch. The waits are heavily CPU biased, but the total waits are low. Cluster is an almost invisible line on the GRID graph. Our ASH reports look fine.

During the crunch time, the users report long delays for report requests and row updates.
Ash reports the Top DB Objects as follows:

Index -  "gc current block 2-way"  activity 16.3%   event 16%
Index -  "db file sequential read"   activity   5.22% event 5%
Table -  "db file sequential read"   activity   2.58% event 2.5%
Table -  "db file sequential read"   activity   1.3%  event .77%
Index -  "db file sequential read"   activity   1.2%  event .98%

When I monitor the system via GRID, I see that CPU is about 60% of the activity. Cluster is about 25%. We see "gc current block 2-way" a good bit.

One of our Top SQL Statements is a select using 37% of activity. It has event percents = 20% "CPU and Wait for CPU" and 16% "gc current block 2-way".

Thanks in advance Received on Tue Jun 05 2007 - 18:14:04 CDT