Re: Latch / Wait Events

1. "rdbms ipc mesage" is idle event experienced by Oracle background processes (DBWR, SMON, PMON, etc) and it can be ignored.
2. "log file parallel write" is event experienced by log writer. It is not experienced by application sessions.

Start from examining V$SESSION_EVENT/V$SESSTAT for sessions created by application.
Let's say a session was connected 1000 seconds ago. It spent:
- 100 seconds on CPU

• 100 seconds on 'db file sequential read/db file scattered read"
• less than 10 seconds on other non-idle events (buffer busy/latch free, etc)
• idle rest of the time (SQL*Net message from client) This indicates healthy session

Let's say a session was connected 1000 seconds ago. It spent:
- 300 seconds waiting on 'latch free'

• 100 seconds on CPU
• 50 seconds on other non-idle events
• idle rest of the time This indicates latch issue.

In other words: start from comparing time spent on various wait events. Received on Sat Nov 14 2009 - 17:47:37 CST