RE: wait events

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>We are getting large waits for 'db file sequential
>read' and 'db file scattered read' on the production
>system. How has your individual experience been on
>changing (increase/decrease) the db_block_buffers and
>db_file_multiblock_read_count in such cases ?

Deepak,

What is your platform? If UNIX, check the output of 'vmstat' and 'iostat' at times of high activity? (ignore first line/set from these two commands as they are the cumulative values from system reboot). If you see a high IOWAIT on 'vmstat', you can use 'iostat' to measure the I/O on individual disks. Tie this to output of V$FILESTAT to identify if indeed these are related to DB File IO. Identify hot-spot tablespaces/datafiles/tables and move them around. In the longer term, you will need to identify the Top SQLs based on Disk Reads and tune them iteratively...

You need to have TIMED_STATISTICS = TRUE set for this instance - I assume you already have this set.

Hth,
John Kanagaraj
Brunei Shell Petroleum
http://www.geocities.com/john_sharmila

God so loved the world that He didn't send a committee! (See John 3:16 for details)
** Opinions expressed here are solely mine and not necessarily those of my employer **

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