LGWR

If you are using Oracle Database Appliance (ODA) then this patch is very important to apply. The patch bundle 2.1.0.3.0 has been published just this week and the most important fix from my perspective is the new BIOS version 12010304. Intel CPUs have a feature called Software Controlled Clock Modulation that allows programmatically control of [...]

Introduction

There was a question about the wait event ‘rdbms ipc message’ in Oracle-l list. Short answer is that ‘rdbms ipc message’ event means that a process is waiting for an IPC message to arrive. Usually, this wait event can be ignored, but there are few rare scenarios this wait event can’t be completely ignored.

What is ‘rdbms ipc message’ wait means?

It is typical of Oracle Database background processes to wait for more work. For example, LGWR will wait for more work until another (foreground or background ) process request LGWR to do a log flush. In UNIX platforms, wait mechanism is implemented as a sleep on a specific semaphore associated with that process. This wait time is accounted towards database wait events ‘rdbms ipc message’.

Also note that, semaphore based waits are used in other wait scenarios too, not just ‘rdbms ipc message’ waits.

Time to Trace

I will be conducting a 1-hour deep dive session about RAC LMS process (and about LGWR processes too if time permits) using advanced UNIX utilities. Read Tanel’s blog entry for details:
RAC hack session

See you there!