Re: which system call is used to measure wait time ?

From: Steve Adams <steve.adams_at_ixora.com.au>
Date: Wed, 31 Jan 2001 00:55:40 GMT
Message-ID: <3a775f62.1980448123@nsw.nnrp.telstra.net>

Hello Danisment,

Oracle uses the gettimeofday() system call to measure wait times. See http://www.ixora.com.au/q+a/0009/15101606.htm for more on that.

Your wait_time is wrong because you are using V$TIMER. Calls to V$TIMER read an SGA data structure. That value only changes when Oracle gets around to updating it, and so it can lag behind real time by a second or more under heavy CPU load. See http://www.ixora.com.au/q+a/0008/29072854.htm for more on that.

@ Regards,
@ Steve Adams
@ http://www.ixora.com.au/
@ http://www.christianity.net.au/

-----Original Message-----
From: danisment_at_yahoo.com

hello,

which system call is used to measure wait time ?

I guess following method is wrong:

t0 := get_time_from_v$timer;
wait();
t1 := get_time_from_v$timer;
wait_time := t1 - t0;

wait_time may show wrong becasue CPU may be still used by process during wait() because of tight loop or OS timer signal SIGALRM to check resource is available.

regards...

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http://www.deja.com/ Received on Tue Jan 30 2001 - 18:55:40 CST