RE: Rman io done waits and the rate parameter

From: DENNIS WILLIAMS <DWILLIAMS_at_LIFETOUCH.COM>
Date: Mon, 20 Dec 2004 12:53:09 -0600
Message-ID: <DFA54221DF26D911BC5100B0D079D97A019B64F7@exchmn5>

Fuad

Statspack summarizes waits in two dimensions - over the time period between snapshots, across all processes on the server. So be careful about drawing conclusions from Statspack reports.

I don't use RMAN to write to tape. However, in reading the RMAN documentation, it appears the main problem is keeping the tape buffer filled so the tape can keep moving. Apparently a tape drive gets really slow if the tape has to stop and restart. Most tuning is oriented toward getting more I/O flowing to the tape drive. So if you are trying to slow down the amount of data flowing to the tape, you may end up with greater problems.

When you say application timings go up by 20% when RMAN is running, I'm assuming you are saying that the RMAN activities seem to be slowing the other applications down.

Perhaps you can run RMAN at a time when it will interfere less with the application.

Consider running a 10046 trace on the application with and without RMAN executing, and see what wait times are different. This may help you pinpoint the interference.

Also, gather statistics at the O/S level with and without RMAN running. I would expect many of the most important effects might not be seen within Oracle itself, but only at the O/S.

Dennis Williams
DBA
Lifetouch, Inc.

-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Fuad Arshad
Sent: Monday, December 20, 2004 8:37 AM
To: oracle-l_at_freelists.org
Subject: Rman io done waits and the rate parameter

we are having very high iodone waits.
and i was wonderign if somone on a list has had to go thru the same issues

thisis a snap from the statspack reports.

                                                                   Avg
                                                     Total Wait   wait
Waits
Event                               Waits   Timeouts   Time (s)   (ms)

/txn
---------------------------- ------------ ---------- ---------- ------

io done                         7,318,903  5,192,927    122,807     17
146.5
sbtwrite2                       4,240,771          0    126,120     30
84.9
io done                         7,318,903  5,192,927    122,807     17

146.5

currently we are on gen1 tape drive plannign to move to gen2's the backup of a 1 tbte database takes around 4 hours but the application timings go up by 20%

i am also looking at ways people have had to use the rate or the readrate parameter to throttle down the amount of i/o and tune down rman.

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http://www.freelists.org/webpage/oracle-l Received on Mon Dec 20 2004 - 12:53:10 CST