RE: Researching latch efficiency

From: Yong Huang <>
Date: Sat, 21 Jun 2008 06:21:10 -0700 (PDT)
Message-ID: <>

Anjo Kolk's wait event article is still the most complete about documenting latches. Search for it on Google.


There is a pool of message blocks in the SGA. This pool is controlled by the init.ora parameter _messages. If a process needs a message it will get the latch, search a linked list for a free message block, unlink this message block , put this message on the message queue for the intended process and then release this latch. The event rdbms ipc message indicates that a process is waiting for a message to arrive on his message queue. The event rdbms ipc message reply is used to indicate that a message is expected back by the sending process.

Why not compare the numbers in Spotlight and sqlplus? If they're close, they must be referring to the same event.

Yong Huang

> I'm using Quest's Spotlight and wonder if it means "latch: messages". I
> may need to open a ticket with Quest Support to explain the display in
> their GUI.
> Not sure if this is the one I'm waiting on. I'll look deeper.
> sql> select * from v$event_name where name = 'latch: messages';
> The online Oracle doc referenced by Jared (thanks J!) does not have all
> 889 wait events documented for I doubt I'm gonna find it. :-)

Received on Sat Jun 21 2008 - 08:21:10 CDT

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