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Re: db file sequential read, where does it read to?

From: Charles Hooper <hooperc2000_at_yahoo.com>
Date: 1 Nov 2006 13:48:00 -0800
Message-ID: <1162417680.236127.297130@m73g2000cwd.googlegroups.com>


Ben wrote:
> 9.2.0.5 Ent Ed AIX5L
>
> I've got a few long running processes that are all performing full
> table scans and they are waiting on db file % reads. When a file read
> is performed, is it reading the blocks into the buffer and then on to
> the user or does it just dump them straight out to the user? What I'm
> getting at is, Could these table scans be aging each other's blocks out
> of the buffer and thus causing more file reads?
> I guess if I could do away with the table scans in general that would
> solve my problem though...
>
> I hope that wasn't too confusing.

DB File Scattered Reads are associated with full table scans, contrary to what the wait event name implies. DB File Sequential Reads are associated with single block reads, usually reading indexes. Blocks read end up in the buffer cache before the contents of the blocks are compared/utilized by Oracle.

Charles Hooper
PC Support Specialist
K&M Machine-Fabricating, Inc. Received on Wed Nov 01 2006 - 15:48:00 CST

Original text of this message

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