Re: [.] RE: Tbs READ ONLY and Snapshot too old

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Sat, 19 Jun 2004 08:44:04 +0100
Message-ID: <00e601c455d1$32194820$7102a8c0@Primary>

A tablespace can only be made read-only after all active transactions that started BEFORE the read-only call have committed. Consequently, no transactions or query that starts after the tablespace is read-only needs to do anything about read-consistency, delayed block cleanout, or commit-time checking.

HOWEVER - queries that started before the tablespace went readonly (or sessesions that set transaction read only) could still be running after the tablespace went read-only, and these need could to apply undo. This is why "after a sufficient period of time" the problem stops happening.

The problem can't happen in a read-only
database because the only way to make a
database read-only is to stop and restart it (I think) so every query has to have started after the database (all tablespaces) became read-only.

Regards

Jonathan Lewis

http://www.jlcomp.demon.co.uk

http://www.jlcomp.demon.co.uk/faq/ind_faq.html The Co-operative Oracle Users' FAQ

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Original Message ----- From: "Gene Sais" <Gsais_at_co.palm-beach.fl.us> To: <psinger1_at_ford.com>; <oracle-l_at_freelists.org> Sent: Thursday, June 17, 2004 6:14 PM Subject: [.] RE: Tbs READ ONLY and Snapshot too old

: Would this apply to a read-only database as well? I haven't seen it in
: my read-only database, has anyone discovered this error?
:
: >>> psinger1_at_ford.com 6/17/2004 12:34:45 PM >>>
: Actually, you are both right.
:
: Delayed Block Cleanout can cause an ORA-1555, even in a read only
: tablespace.
:
: However, if the tablespace has been read only "for a long enough period
: of time",
: every query against it will realize that all updates to objects in that
: tablespace have
: been committed, and will never try to reconstruct the table.

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Received on Sat Jun 19 2004 - 02:40:48 CDT