John,
read my post...Modified blocks are written to the REDO LOGS. After the END
BACKUP is issued and at the next log switch, the changed blocks are then
updated in the datafiles. It is such an easy concept to grasp, yet so many
DBA's are confused about this procedure. Maybe I'm wrong, but I would hate to
believe that I paid $1400 dollars to Oracle Education to mislead me on Backup
and Recovery.
Satar Naghshineh
In article <36115B13.89938F9D_at_deere.com>,
"John P. Higgins" <jh33378_at_deere.com> wrote:
> <HTML>
> It is true: Oracle stops updating file headers durring backup mode.
>
> <P>It is also true: Oracle writes changed blocks to the files durring backup
> mode.
>
> <P>satar_at_my-dejanews.com wrote:
> <BLOCKQUOTE TYPE=CITE>OK, I think everyone is confused. According to
"Oracle7:Backup
> and Recovery
> <BR>Volume Two * Student Guide" which I obtained durring my DBA Master's
> program
> <BR>held by Oracle Corporation, on page 10-13 through page 10-17 it tells
> you the
> <BR>following: After you administer BEGIN BACKUP...This action suspends
> updates
> <BR>to the header block of each database file belonging to the Tablespace.
> If a
> <BR>log switch occures, the sequence number information is updated as shown.
> A
> <BR>record is also written to the active redo log file to indicate that
> an online
> <BR>backup has begun. END BACKUP...This action will cause the header blocks
> for
> <BR>the datafiles belonging to the tablespace to be updated at the next
> log
> <BR>switch. If a log switch occures, the sequence number information is
> updated
> <BR>as shown. * The time between the ALTER BEGIN and ALTER END commands
> should be
> <BR>minimized, as more redo information is generated and written to the
> redo log
> <BR>files durring the backup since modified blocks are written to the redo
> log
> <BR>files. * Prior to Oracle7 release 7.2, any instance faliur while an
> online
> <BR>backup was in progress could cause the subsequent automatic recovery
> at
> <BR>startup to fail due to the header on the backed up file being frozen.
> Oracle7
> <BR>at startup would then detect that the header was out of sync with the
> rest of
> <BR>the files, and startup would fail with the message the file needed
> recovery.
> <BR>New to release 7.2, you can allow an online backup to be ended before
> opening
> <BR>the database after a system failure, by executing the ALTER DATABASE
> DATAFILE
> <BR>END BACKUP command.
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Received on Wed Sep 30 1998 - 13:50:58 CDT
