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RE: Capacity Planner from OEM VS Statspack

From: MacGregor, Ian A. <ian_at_SLAC.Stanford.EDU>
Date: Mon, 02 Feb 2004 12:57:42 -0800
Message-id: <26E3EC48949D134C94A1574B2C89466113A6E2@exchange2.slac.stanford.edu>


What do you do when someone calls to say, "My job which usually takes 20 minutes to run took over 2 hours last night?" Do you inquire about the composition of the job and immediately run a 10046 trace on it? The information from that trace may not represent what is happened the prevous night because the conditions such as the load on the database are different. However with statspack information I might see that the number of direct path reads and writes went up significantly during that period from their norm, and the waits also increased. Remember the information is collected every 10 minutes I can now get the plan information as well. Is there a hash join. Time to check the statistics.

Perhaps the problem is not being caused by the program the person is calling about, but by another. Statspack can be helpful here as well. If I cannot figure it out I can still try tracing the program or set a login trigger to start the trace when the job runs that night. Of course Ideally I should have already collected a job profile ...

Something like

Call                                 Duration         Calls      Duration/Call
------------------------------------------------------------------------------
direct path write                   95.28s  81.1%      5707      0.02s
direct path read                    21.47s  18.3%      7632      0.00s
SQL*Net message from client          0.59s   0.5%         4      0.15s
db file scattered read               0.17s   0.1%       652      0.00s
SQL*Net message to client            0.00s   0.0%         4      0.00s
db file sequential read              0.00s   0.0%         1      0.00s

Total cpu time: 30.5 seconds

And be ready to compare it with what the new trace delivers.

Finally there are some jobs which manipulate data which are impossible to repeat because the data has changed. What do you run the 10046 trace on then?

Statspack is certainly no 10046 trace, but it is not useless.

Ian MacGregor
Stanford Linear Accelerator Center
ian_at_SLAC.Stanford.edu   

-----Original Message-----
From: Andy Rivenes [mailto:arivenes_at_llnl.gov] Sent: Monday, February 02, 2004 10:51 AM To: oracle-l_at_freelists.org
Subject: RE: Capacity Planner from OEM VS Statspack

However, what you're really collecting is "workload" information. It's only useful, as Cary stated, for capacity planning, or what you stated, for trends. You're not going to solve a "performance" problem with this level of information.

Andy Rivenes
arivenes_at_llnl.gov

At 10:00 AM 2/2/2004 -0800, MacGregor, Ian A. wrote:
>I have to disagree here. Sometimes one needs to take a top-down
>approach
>to tuning. Measuring things such as CPU usage and I/O counts can be
>useful. For instance here's a report for a very lightly loaded system
>based on statspack data.
>
>
>DATABASE BEGIN_TIME END_TIME Physical Reads
>Physical Writes CPU SECONDS ELAPSED SECONDS
>---------- -------------------- -------------------- --------------
>--------------- ----------- ---------------
>ORAP 12-JAN-2004:00:00:03
>12-JAN-2004:01:00:05 14725 7697 224.005
>3602
>ORAP 12-JAN-2004:01:00:05
>12-JAN-2004:02:00:02 6271 2125 5.03
>3597
>ORAP 12-JAN-2004:02:00:02
>12-JAN-2004:03:00:04 66066 1043 6.105
>3602
>ORAP 12-JAN-2004:03:00:04
>12-JAN-2004:04:00:02 1496 1125 3.68
>3598
>ORAP 12-JAN-2004:04:00:02
>12-JAN-2004:05:00:04 1716 1462 3.995
>3602
>ORAP 12-JAN-2004:05:00:04
>12-JAN-2004:06:00:01 961 1721 3.71
>3597
>ORAP 12-JAN-2004:06:00:01
>12-JAN-2004:07:00:03 3779 1032 3.985
>3602
>ORAP 12-JAN-2004:07:00:03
>12-JAN-2004:08:00:06 16436 2026 5.84
>3603
>ORAP 12-JAN-2004:08:00:06
>12-JAN-2004:09:00:03 231051 2634 14.43
>3597
>ORAP 12-JAN-2004:09:00:03
>12-JAN-2004:10:00:05 137762 1245 15.605
>3602
>ORAP 12-JAN-2004:10:00:05
>12-JAN-2004:11:00:03 183870 1163 15.21
>3598
>ORAP 12-JAN-2004:11:00:03
>12-JAN-2004:12:00:05 143757 1166 12.975
>3602
>ORAP 12-JAN-2004:12:00:05
>12-JAN-2004:13:00:02 20349 1088 4.705
>3597
>ORAP 12-JAN-2004:13:00:02
>12-JAN-2004:14:00:04 195781 1827 13.355
>3602
>ORAP 12-JAN-2004:14:00:04
>12-JAN-2004:15:00:02 26901 1538 9.53
>3598
>ORAP 12-JAN-2004:15:00:02
>12-JAN-2004:16:00:04 43434 1039 8.205
>3602
>ORAP 12-JAN-2004:16:00:04
>12-JAN-2004:17:00:01 61892 1747 8.485
>3597
>ORAP 12-JAN-2004:17:00:01
>12-JAN-2004:18:00:04 36268 819 5.99
>3603
>ORAP 12-JAN-2004:18:00:04
>12-JAN-2004:19:00:01 87842 1302 8.4
>3597
>ORAP 12-JAN-2004:19:00:01
>12-JAN-2004:20:00:03 1256 653 4.625
>3602
>ORAP 12-JAN-2004:20:00:03
>12-JAN-2004:21:00:01 197415 1086 99.765
>3598
>ORAP 12-JAN-2004:21:00:01
>12-JAN-2004:22:00:03 556 1386 3.235
>3602
>ORAP 12-JAN-2004:22:00:03
>12-JAN-2004:23:00:06 1074 697 3.22
>3603
>ORAP 12-JAN-2004:23:00:06
>13-JAN-2004:00:00:03 14856 927 4.495
>3597
>ORAP 13-JAN-2004:00:00:03
>
>
>
>If I have a report which deviates from this, then I can start
>looking more closely. The statspack information is gathered every ten
>minutes. I can then propely trace the statements which are candidate
>problems. I can also get more information. If the CPU count goes up is
>it due to an increase of logical I/Os. How much of the physical I/O is
>direct and to what tablespaces etc.
>
>There are many problems with statspack and the virtual views upon which
>it
>is based. Counters resetting are going negative, the frequency of the
>updates etc. I have made elaborate systems, chucked them out of
>frustration, changed tactics and tried again.
>
>At one time I was totally against such systems because they were not
>perfect, actually far from it. But I came to realize that though
>statspack is inadequate, it is not useless.
>
>Ian MacGregor
>Stanford Linear Accelerator Center
>ian_at_SLAC.Stanford.edu



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Received on Mon Feb 02 2004 - 14:57:42 CST

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