Re: Can anyone explain this huge increase in logical I./O....?

> Compare the VALUE column of first and second run of the above query.
> Changed values will give you an idea of what is happening in the
> database, for instance undo being applied to blocks to provide a
> consistent read. The Oracle manuals explain what each of the
> statistics mean. For examples:
> CONSISTENT GETS: Statistic counts the number of logical reads in
> consistent mode.
> CONSISTENT CHANGES: Statistic indicates the number of times a
> database block has rollback entries applied to perform a consistent
> read of the block. Work loads that produce a great deal of consistent
> changes can consume a great deal of resources. The value of this
> statistic should be small in relation to the 'consistent gets'
> statistic.
> DATA BLOCKS CONSISTENT READS - UNDO RECORDS APPLIED: Number of undo
> records applied to data blocks that have been rolled back for
> consistent read purposes.
> CLEANOUTS AND ROLLBACKS - CONSISTENT READ GETS: Number of consistent
> gets that require both block rollbacks and block cleanouts.

This is excellent feedback - thanks for your help. I will use the before and after values to determine whether it is in fact 'consistent changes' which are causing the huge increase in logical I/O.

Thanks for your help.

Matt Received on Tue Oct 24 2006 - 02:06:39 CDT