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

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

http://www.jlcomp.demon.co.uk/seminar.html
Optimising Oracle Seminar - schedule updated May 1st


----- Original Message ----- 
From: "Gene Sais" <Gsais@xxxxxxxxxxxxxxxxxxx>
To: <psinger1@xxxxxxxx>; <oracle-l@xxxxxxxxxxxxx>
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@xxxxxxxx 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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