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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Performance Problem after Migration
Scott - I would approach this as a standard tuning problem, and try to avoid
making assumptions about what the answer is. Find out what the system waits
are. STATSPACK is pretty good at listing your waits. Otherwise, there are
scripts available that you can run. Make sure the database is waiting for
what you assume it is. If the predominant waits are for the disk subsystem,
then you will investigate that further. Also, are you sure the application
wasn't changed sometime over the migration?
Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com
-----Original Message-----
Sent: Thursday, August 01, 2002 4:28 PM
To: Multiple recipients of list ORACLE-L
I have an interesting problem. I recently migrated a database from a Digital Unix system to a Sun Solaris system, with an EMC disk array. Since I was going to be migrating the database, I decided to double the block size from 4k to 8k. I also created the tablespaces on the new box as locally managed, with fixed extent sizes. Then I did a full database export, ftp'd the file, and imported it. It went well, or so I thought. The application works, but it is much slower than it was on the original (Digital) system.
One side effect was that I didn't change the db_block_buffers, so that part of the SGA essentially doubled in size. The library cache hit rate was always around 99%, but the data cache hit rate used to only be about 85%, now it is 95 - 99%. All of the sorts are being done in memory, with memory to spare (52G yesterday, not used). According to the statistics, the database should be screaming. But the users are complaining that the online screens are taking much longer to come up. They say that the screens used to come up in 1 - 2 seconds, now it's taking about 10.
Just for fun, I tried deleting the statistics and changing the optimizer_mode from choose to rule. That made things worse, which was what I expected, but it was worth a try. I have tried to capture a session, but I need to get a repository up to look at the trace that was generated. Until then, I'm pretty baffled. I'd appreciate any ideas that anyone has on this.
Thank you.
--
Scott Canaan (srcdco_at_rit.edu)
(585) 475-7886
"Life is like a sewer, what you get out of it depends on what you put
into it" - Tom Lehrer
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Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Scott Canaan
INET: srcdco_at_ritvax.rit.edu
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