| Oracle 9i Performance Doubts [message #64827] |
Tue, 17 February 2004 04:04  |
Prasad
Messages: 104
Registered: October 2000
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Senior Member |
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Hi All,
IS there any command or method to find out what is the maximum IO permitted on unix(SUN and HP) and Linux and NT platforms. optimizer_index_caching(<100) which favours Nested loops and Optmizer_index_cost_adj(<100) which favours Index scans.Suppose If set db_file_multiblock_read_count=32 still I am seeing the good performance.that is still it is using Index scans. My next question is db_file_multiblock_read_count=32 help in fetching index blocks with less IO.
My third question is Which Parameters I have to look in statspack to find the diffrence for setting of these parameters(optimizer_index_caching and Optmizer_index_cost_adj). and also
please advice me what more parameters I have set to use to drive oracle for better performance.Since I have only control from database not much from application.Most of the things driven from java/corba stuff.
1)optimizer_max_permutations=1000
2)optimizer_mode= first rows Since it fetches results fast for fewer records may go suboptimal plans and all rows favours full table scans (advice me here)
3) pga_aggregate_target=200m
4) workarea_size_policy=auto.
What more parameters I have to set in the initalization paramerts.
and 4th Question is in Donlad Burleson articles says that setting log_buffer > 4M is of not much use.
(http://builder.com.com/5100-6388-5035207.html)
But I may predict the redolog space requests and redo allocation retries will increase if I am reducing redolog buffer u'r advice on this.
Finally in rollback segments we were assigning bigger rollback segment for any large jobs how the same thing is taken care in undo_tablespace. If I am setting too much undo_retention this will be applicable for all the undo segments which I feel waste of space.I am quite curious to know is anyway we can provide large chunk of space for paritcular undo segment.
Thanks and Regards
Prasad
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