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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