Re: Latches
From: joel garry <joel-garry_at_home.com>
Date: Fri, 9 Oct 2009 14:19:05 -0700 (PDT)
Message-ID: <44ca99d9-aa0c-4818-b24b-ed968f37eee0_at_b25g2000prb.googlegroups.com>
On Oct 9, 10:32 am, The Magnet <a..._at_unsu.com> wrote:
> Hi,
>
> Been looking around and reading on latches. I see references to
> 'parent' and 'child' latches. I'd like to understand the difference
> but I cannot find any good documentation on them. The Oracle
> documentation did not really explain why one would be acquired over
> the other.
>
> Thanks.
>
> Oh yeah, Sybrand, anything?
Date: Fri, 9 Oct 2009 14:19:05 -0700 (PDT)
Message-ID: <44ca99d9-aa0c-4818-b24b-ed968f37eee0_at_b25g2000prb.googlegroups.com>
On Oct 9, 10:32 am, The Magnet <a..._at_unsu.com> wrote:
> Hi,
>
> Been looking around and reading on latches. I see references to
> 'parent' and 'child' latches. I'd like to understand the difference
> but I cannot find any good documentation on them. The Oracle
> documentation did not really explain why one would be acquired over
> the other.
>
> Thanks.
>
> Oh yeah, Sybrand, anything?
http://lmgtfy.com/?q=%22Parent+and+child+latches%22+%2Bsteve+%2Badams
Basically, child latches are used to protect SGA memory areas with a finer granularity than in previous versions. For example, the library cache latch serializes access to objects there. If you have a latching problem, and you make the library larger, you just make the latching problem worse (like in O8). So Oracle makes 7 child latches to protect various parts in 9i. Then does more stuff in 10g. Now http://blog.tanelpoder.com/2008/08/03/library-cache-latches-gone-in-oracle-11g/ If you want to dig deep and see some cool examples, search for latch on tanel's blog.
jg
-- _at_home.com is bogus. http://www3.signonsandiego.com/stories/2009/oct/09/mom-who-toted-gun-shot-killed-home/?uniontribReceived on Fri Oct 09 2009 - 16:19:05 CDT