Re: wait events and v$session

From: <Jared.Still_at_radisys.com>
Date: Tue, 11 May 2004 13:45:35 -0700
Message-ID: <OFBAA0FB31.8F2B02F7-ON88256E91.0071420E-88256E91.00720A31@radisys.com>

wait time vs. service time has appeared here a few times lately. I believe Cary addressed this in another thread today.

service time = amount of time required to complete a task.

eg. db_file_scattered read.

wait time = amount of time spent waiting for a resource to become available

eg. buffer busy waits

Oracle reports disk reads as wait events, but the time includes service time.

Jared

<ryan.gaffuri_at_cox.net>
Sent by: oracle-l-bounce_at_freelists.org
05/11/2004 07:32 AM
Please respond to oracle-l

        To:     oracle-l_at_freelists.org
        cc: 
        Subject:        wait events and v$session_event

I have one batch process running and there are alot of waits. I thought waits were caused by concurrency?

If this is unreadable, please ignore. Hard to format with web email. Basically, I have large waits for DB_FILE_SCATTERED_READ, DB_FILE_SEQUENTIAL_READ, and for RAC Cache Fusion due to the load balancing.

     SID EVENT                          TOTAL_WAITS TOTAL_TIMEOUTS

TIME_WAITED AVERAGE_WAIT MAX_WAIT TIME_WAITED_MICRO
---------- ------------------------------ ----------- --------------

------------ ---------- ----------------- 22 rdbms ipc reply 1 0 0 0 0 165 22 log file sync 1 0 0 0 0 996 22 db file sequential read 491250 0 23237 0 172 232371459 22 db file scattered read 159243 0 29892 0 37 298924960 22 global cache open x 10 0 0 0 0 3380 22 global cache s to x 11273 0 648 0 42 6477337 22 global cache cr request 1453244 16 233740 0 98 2337401155 22 row cache lock 210 0 14 0 0 135414 22 library cache lock 15 0 1 0 0 5311 22 SQL*Net message to client 21 0 0 0 0 27 22 SQL*Net message from client 21 0 1 0 0 9023

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Received on Tue May 11 2004 - 15:42:58 CDT

Re: wait events and v$session_event