RE: many seconds waiting for I/O?
- From: "Dunbar, Norman" <norman.dunbar@xxxxxxxxxxxxxxxxxxxxxxxxx>
- To: <ax.mount@xxxxxxxxx>, "oracle-l" <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 27 Jul 2007 11:35:04 +0100
Morning Alex,
>> I have a batch process running and it seems that it's
>> waiting for I/O all the time, the strange thing is it shows
>> 400 seconds waits!
>>
>> EVENT CONSISTENT_GETS SPID
>> WAIT_TIME SECONDS_IN_WAIT STATE SEQ#
>> -------------------------- --------------- ------------
>> ---------- --------------- ------------------- ----------
>> db file sequential read 212532 25879
>> -1 374 WAITED SHORT TIME 892
The STATE of 'waited short time' and the WAIT_TIME of -1 show that this
is not waiting.
The values of WAIT_TIME are :
Negative : the wait time was unknown.
Zero : the session is still waiting.
Positive : the actual time waited.
PLUS for a session that is waiting, the STATE will be 'WAITING'.
You have to take STATE, WAIT_TIME and SECONDS_IN_WAIT together.
A STATE of 'waited short time', as you have, means that the actual wait
was less than one cent-second and the WAIT_TIME is always shown as -1.
The WAIT_TIME you see is the session's LAST wait time - so whatever
event it was waiting on previous to the current one would have waited
nearly 400 seconds. I'd be willing to say that in a batch program it
would be something like 'SQL*NET message from client' as Oracle has fed
the batch program a shed load of data which it has to process before
doing the next lot/query.
Obviously, you'd want to trace the session to be 100% sure ....
HTH
Cheers,
Norman.
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