RE: Oracle Internals

From: Henry Poras <Henry.Poras_at_ctp.com>
Date: Wed, 14 Mar 2001 10:15:30 -0800
Message-ID: <F001.002CC5D6.20010314080032@fatcity.com>

RM,
Thanks. Intuitively that seems like the way it should work. However it appears to contradict what Steve wrote in his book about a sleeping process waiting on its semaphore. I wonder if this is just a publishing error, or if I am missing something in my understanding. I usually find it a good policy to give Steve Adams the benefit of the doubt.

Henry

-----Original Message-----
Sent: Wednesday, March 14, 2001 9:06 AM
To: Multiple recipients of list ORACLE-L

HP, it is sleep/wake/check. it is up to the process to acquire the resource. AFAIK, there is no message-passing type of algorithm to tell waiting (whether spinning or sleeping) processes when the semaphore becomes unset ( ie the resource is available ) Sleeps are expensive in Latchville, and you can track their occurence via v$latch_waits and the SLEEP* columns.

hope this partial answer helps.

-----Original Message-----
]
Sent: Tuesday, March 13, 2001 10:25 PM
To: Multiple recipients of list ORACLE-L

I have been rereading Steve Adam's book a bit more carefully and have a question. Just wondering if anyone has any answers.

When talking about latch sleeps, the book states "a process sleeping for a latch waits on its semaphore". However, latches don't support queuing and a number of processes may be waiting for the same latch. If I am sleeping and the latch frees, who knows I need that semaphore? Are all waiting processes posted with the semaphores going on/off/on/off? or is no semaphore posted and the processes go sleep/wake/check/sleep/wake/check? I can't quite picture the details here.

Henry

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Author: Henry Poras
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Author: Henry Poras
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