Re: High db file sequential reads during imp?
- From: Joerg Jost <joerg.jost@xxxxxxxxxxxx>
- To: kadmon@xxxxxxxxx
- Date: Fri, 09 May 2008 11:30:49 +0200
Am Freitag, den 09.05.2008, 08:22 +0100 schrieb cam:
> Hello all,
>
> Relative newcomer to performance analysis. I was surprised, upon
> investigating a very slow import job, to find very high 'db file
> sequential read's. This activity was mostly associated with an index
> that was being updated while around 11 million rows were inserted to a
> normal heap table. I'm clearly missing something obvious here but why
> would imp be reading (and not writing?) so heavily from this index?
>
> Regards,
> cam
Hi,
i think, you give the answer with the question, if i am right.
Imp will insert a lot of rows. Depending on the configuration of the imp
(commit=?) it will upgrade the indexes associated with the table you're
inserting.
To do this, imp has to read the table. This are the db file sequential
reads you have discovered i think.
You should try to disable commit with the above mentioned configuration
parameter. If the import is still slow, try indexes=n and afterwards
another imp - job with indexfile=/bla/blub.sql
Then you will get a file with the statement(s) to build the indexes
after inserting every row into the table. This can be considerably
faster.
hth
Jörg
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