There are several scenarios that can occur in an Oracle Data
Guard configuration which renders a physical standby database as either
unusable or invalid. For example, an extended network failure can occur between
the primary and standby machines which cause the standby database to fall
significantly far behind the primary database. If the necessary archived redo
log files needed to synchronize the physical standby database with the primary
database are no longer available, log gap resolution will be unable to resolve
the gap in the redo stream to catch up the standby.
1. On
the physical standby database, stop the managed recovery process (MRP):
SQL> alter database recover managed standby database cancel;
2. On
the physical standby database, find the SCN which will be used for the
incremental backup at the primary database, as the backup must be created from
this SCN forward.
SQL> select
current_scn from v$database;
CURRENT_SCN
-----------
3744425
3. Record
the SCN returned from the above query for the next step.
4. Using
RMAN, connect to the primary database and create an incremental backup from the
SCN derived in the previous step.
RMAN>
backup incremental from scn 3744425 database format '/u01/bkp/ForStandby_%U.inc' tag 'FORSTANDBY';
5.
Create new standby controlfile on production
database.
SQL>alter database create standby
controlfile as
'/u01/bkp/CONTROL01.CTL’;
6.
Ship all the incremental backups and new standby
controlfile to DR site. Let me assume that we have created '/u01/bkp/’
directory at DR site also to keep all the incremental backups and new standby
controlfile.
7.
After copying the
incremental backup pieces to the physical standby machine, connect to the
physical standby database using RMAN and catalog those incremental backup
pieces. Then recover the standby database with the cataloged incremental backup
pieces.
RMAN>
catalog start with '/u01/bkp/’;
RMAN> recover database noredo;
8.
Shutdown the standby database and rename all the
old standby controlfiles.
Replace all the old standby controlfile
with new ones that you have brought from production site.
RMAN> shutdown;
9.
Now we can start the physical standby database.
RMAN>
startup mount;
10.
Keep physical
standby database again in managed
recovery mode and take some
Manual log switches at production site to see whether archives are
transferring to
Recovered standby and applying or not. Wait and test again.
SQL>alter database recover managed standby
database disconnect from session;
SQL>select sequence#, archived, applied
from v$archived_log;
