Re: URGENT! Writes to Disk while Doing a SELECT statement?

From: Peter Sharman <psharman_at_us.oracle.com>
Date: Wed, 03 Feb 1999 12:55:03 -0800
Message-ID: <36B8B7A6.BC5C3092@us.oracle.com>

Jonathan

I'm somewhat confused by what you said. DELAYED_LOGGING_BLOCK_CLEANOUTS turns the delayed block cleanout feature on or off. Keeping this feature set to TRUE sets a fast path, no logging block cleanout at commit time. Logging the block cleanout occurs at the time of a subsequent change to the block.

When Oracle commits a transaction, each block that the transaction changed is not immediately marked with the commit time. This is done later, on demand, when the block is read or updated.

In other words, the default mechanism means that a select statement SHOULD cause cleaned blocks to be written, at least to my understanding.

I'd be glad to be corrected if I'm wrong though!

Pete

Jonathan Lewis wrote:

> Peter,
>
> The version is 7.3.4 so the default clean-out mechanism means that
> a select statement should not cause cleaned blocks to be written.
> (delayed_logging_block_cleanouts = TRUE).
>
> Jonathan Lewis
> Yet another Oracle-related web site: www.jlcomp.demon.co.uk
>
> Peter Sharman wrote in message <36B87B07.5A348719_at_us.oracle.com>...
> >Satar
> >
> >You may be seeing the effects of delayed block cleanout, where your SELECT
> >statement is the first statement to hit blocks that have been updated but
> not
> >written out yet.
> >

Regards

Pete

Peter Sharman                              Email: psharman_at_us.oracle.com
WISE Course Development Manager            Phone: +1.650.607.0109 (int'l)
Worldwide Internal Services Education               (650)607 0109 (local)

San Francisco

"Controlling application developers is like herding cats." Kevin Loney, ORACLE DBA Handbook
"Oh no it's not! It's much harder than that!" Bruce Pihlamae, long term ORACLE DBA

Received on Wed Feb 03 1999 - 14:55:03 CST