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From Martin Kalén <mka...@apache.org>
Subject Re: cvs commit: db-ojb/src/java/org/apache/ojb/broker/platforms PlatformOracle9iImpl.java
Date Fri, 25 Feb 2005 19:28:05 GMT
mkalen@apache.org wrote:
>   Lower sizes for Oracle-specific row pre-fetch and statement cache.

Matthew have been advising me (around March 2004) that Oracle reports 
10-15% improvements with their row pre-fetching. I have also heard from 
a DBA attending an Oracle seminar that Oracle recommend row pre-fetch 
with a value of 200.

However, it seems that OJB does not benfit too much from this and the 
memory requirements are just skyrocketing when the JDBC driver starts to 
  prefetch for all it's worth. A customer of my day-job company were 
also getting frequent OutOfMemoryException in production with OJB 1.0.1 
and Oracle row-prefetch=100, this disappeared when lowering this value 
to 10.

I know that Oracle row pre-fetch is complimentary to OJB proxy 
pre-fetch, so both should be kept in place. However it seems that OJB 
gets a much lower footprint without loosing noticeable performance if 
the values are lowered. Today I did some extensive testing and you can 
read the results here (no, I am not a graphics designed and I can't do 
good screenshots - click the method names if you dare...). :-)

http://www.apache.org/~mkalen/ojb/broker-tests.html

Values before commit are boxed in red, current values in green.

Unfortunately I was seeing the occasional failure in 
testRuntimeMetadataChanges (click the links from # failures), that we 
were previously seeing here:
http://mail-archives.apache.org/eyebrowse/ReadMsg?listId=107&msgNo=11589

After the latest Torque vs Oracle DATE/TIMESTAMP discussions I'm 
suspecting that this could in fact be related to a timing issue due to 
some DATE column in the Torque DDL, rather than any Oracle-specific 
optimizations in 9i platform. It is *not* reproducable to first run with 
PlatformOracleImpl and the PlatformOracle9iImpl (as I thought when I 
wrote the mail on the user-list), since it only fails in about 1 out of 
10 runs even with 9i...

Cheers,
  Martin

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