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Home -> Community -> Mailing Lists -> Oracle-L -> Re: [.] RE: Tbs READ ONLY and Snapshot too old
Thank you!
Gene Sais, DBIA
COCC Automation Services Department
205 North Dixie Highway, Room 2.2209
West Palm Beach, FL 33401
P: 561.355.3467 F: 561.355.2600 C: 561.662.2018 [#3] E: Gsais_at_co.palm-beach.fl.us
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/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
: 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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