Re: Researching latch efficiency
- From: Anjo Kolk <anjo.kolk@xxxxxxxxxxx>
- To: <yong321@xxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Sat, 28 Jun 2008 21:45:23 +0200
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$message have the
answers). Hmmm didn't I do a presentation on this 3-4 years ago during IOUG
:)
Anjo.
Op 6/21/08 3:21 PM, Yong Huang <yong321@xxxxxxxxx> schreef:
> Anjo Kolk's wait event article is still the most complete about documenting
> latches. Search for it on Google.
>
> messages
>
> There is a pool of message blocks in the SGA. This pool is controlled by the
> init.ora parameter _messages. If a process needs a message it will get the
> latch, search a linked list for a free message block, unlink this message
> block
> , put this message on the message queue for the intended process and then
> release this latch. The event rdbms ipc message indicates that a process is
> waiting for a message to arrive on his message queue. The event rdbms ipc
> message reply is used to indicate that a message is expected back by the
> sending process.
>
> Why not compare the numbers in Spotlight and sqlplus? If they're close, they
> must be referring to the same event.
>
> Yong Huang
>
>> I'm using Quest's Spotlight and wonder if it means "latch: messages". I
>> may need to open a ticket with Quest Support to explain the display in
>> their GUI.
>>
>> Not sure if this is the one I'm waiting on. I'll look deeper.
>>
>> sql> select * from v$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. :-)
>
>
>
>
>
> --
> //www.freelists.org/webpage/oracle-l
>
>
--
//www.freelists.org/webpage/oracle-l
Other related posts:
