RMAN: Question on database incarnation

From: Kumar Madduri <ksmadduri@xxxxxxxxx>
To: oracle Freelists <Oracle-L@xxxxxxxxxxxxx>
Date: Tue, 20 Jul 2010 06:29:49 -0700

Hello:
The document
http://download.oracle.com/docs/cd/B28359_01/backup.111/b28270/rcmcatdb.htm#BRADV89694
explains
how to reset the incarnation of a database to previous incarnation.
I have couple of questions regarding this.
1. If I do full backups every day (no incremental), does it matter which
incarnation is used (the old or new). From what I understood, it may be that
the current incarnation thinks there was a reset logs at some time and RMAN
uses that (current incarnation) as the marker to determine wh at logs are
required for recovery. But does it matter when I am backing up the entire
database and the archive logs generated every day through RMAN.
2. The document above also gives these additional steps in addition to reset
incarnation to n; I am not sure why the shutdown and reset logs is required
. Would resetting to prior incarnation not be enough especially if you are
not on incremental  backups.

RESET DATABASE TO INCARNATION 2;

 If the control file of the previous incarnation is available and mounted,
then skip to step 6 of this procedure. Otherwise, shut down the database and
start it without mounting. For example:

SHUTDOWN IMMEDIATE
STARTUP NOMOUNT

 Restore a control file from the old incarnation. If you have a control file
tagged, then specify the tag. Otherwise, you can run the SET UNTIL command,
as in this example:

RUN
{
  SET UNTIL 'SYSDATE-45';
  RESTORE CONTROLFILE; # only if current control file is not available
}

 Mount the restored control file:

ALTER DATABASE MOUNT;

 Run RESTORE and RECOVER commands to restore and recover the database files
from the prior incarnation, then open the database with the
RESETLOGSoption. For example, enter:

RESTORE DATABASE;
RECOVER DATABASE;
ALTER DATABASE OPEN RESETLOGS;

Thank you
Kumar

RMAN: Question on database incarnation

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