Re: What's the " latch "

Don't forget that you can queue for a lock, so it's first come , first served.

With a latch, you grab for it, and if you miss it someone else may get it before
you next try to grab. There is no queuing mechanism for latches.

--

Jonathan Lewis
Yet another Oracle-related web site:  http://www.jlcomp.demon.co.uk

Practical Oracle 8i:  Building Efficient Databases
Publishers:  Addison Wesley Longman
Book bound date now 1st Dec 2000

andrewweb wrote in message
<973507018.23110.0.nnrp-04.c30bdde2_at_news.demon.co.uk>...


>A latch is an internal Oracle mechanism used to protect data structures in

>the SGA from simultaneous access. Atomic hardware instructions like

>TEST-AND-SET are used to implement latches. Latches are more restrictive

>than locks in that they are always exclusive. Latches are never queued, but

>will spin or sleep until it obtains a resource or times out.

>

>"Trister Yang" <jonathan_at_ms35.url.com.tw> wrote in message

>news:8u53l2$2du$1_at_news.seed.net.tw...

>> I have read  in oracle concept, but I really  don't know what's the

>> "latch" mean?

>>

>> I will appreciate for any reply!

>>

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