Re: Researching latch efficiency

People,

Symptoms vs problems. Latch waits are always symptoms of the real problem. So this particular latch is a symptom because the shadows sending many messages to the background processes. Normally this would be LGWR and/or the DBWR. Dumping the messages (oradebug dump messages and x$message have the answers). Hmmm didn't I do a presentation on this 3-4 years ago during IOUG :)

Anjo.

Op 6/21/08 3:21 PM, Yong Huang <yong321_at_yahoo.com> schreef:

> Anjo Kolk's wait event article is still the most complete about documenting
> latches. Search for it on Google.
>
> messages
>
> 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 10.2.0.4. I doubt I'm gonna find it.  :-)

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