How to sync standby database which is lagging behind from primary database
Primary Database cluster: cluster1.rmohan.com
Standby Database cluster: cluster2.rmohan.com
Primary Database: prim
Standby database: stand
Database version:11.2.0.1.0
Reason:-
1. Might be due to the network outage between the primary and the standby database leading to the archive
gaps. Data guard would be able to detect the archive gaps automatically and can fetch the missing logs as
soon as the connection is re-established.
2. It could also be due to archive logs getting missed out on the primary database or the archives getting
corrupted and there would be no valid backups.
In such cases where the standby lags far behind from the primary database, incremental backups can be used
as one of the methods to roll forward the physical standby database to have it in sync with the primary database.
At primary database:-
SQL> select status,instance_name,database_role from v$database,v$instance;
STATUS INSTANCE_NAME DATABASE_ROLE
———— —————- —————-
OPEN prim PRIMARY
SQL> select thread#,max(sequence#) from v$archived_log group by thread#;
THREAD# MAX(SEQUENCE#)
———- ————–
1 214
At standby database:-
SQL> select status,instance_name,database_role from v$database,v$instance;
STATUS INSTANCE_NAME DATABASE_ROLE
———— —————- —————-
OPEN stand PHYSICAL STANDBY
SQL> select thread#,max(sequence#) from v$archived_log group by thread#;
THREAD# MAX(SEQUENCE#)
———- ————–
1 42
So we can see the standby database is having archive gap of around (214-42) 172 logs.
Step 1: Take a note of the Current SCN of the Physical Standby Database.
SQL> select current_scn from v$database;
CURRENT_SCN
———–
1022779
Step 2 : Cancel the Managed Recovery Process on the Standby database.
SQL> alter database recover managed standby database cancel;
Database altered.
Step 3: On the Primary database, take the incremental SCN backup from the SCN that is currently recorded on the standby database (1022779)
At primary database:-
RMAN> backup incremental from scn 1022779 database format ‘/tmp/rman_bkp/stnd_backp_%U.bak’;
Starting backup at 28-DEC-14
using channel ORA_DISK_1
backup will be obsolete on date 04-JAN-15
archived logs will not be kept or backed up
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00001 name=/u01/app/oracle/oradata/prim/system01.dbf
input datafile file number=00002 name=/u01/app/oracle/oradata/prim/sysaux01.dbf
input datafile file number=00005 name=/u01/app/oracle/oradata/prim/example01.dbf
input datafile file number=00003 name=/u01/app/oracle/oradata/prim/undotbs01.dbf
input datafile file number=00004 name=/u01/app/oracle/oradata/prim/users01.dbf
channel ORA_DISK_1: starting piece 1 at 28-DEC-14
channel ORA_DISK_1: finished piece 1 at 28-DEC-14
piece handle=/tmp/rman_bkp/stnd_backp_0cpr8v08_1_1.bak tag=TAG20141228T025048 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:25
using channel ORA_DISK_1
backup will be obsolete on date 04-JAN-15
archived logs will not be kept or backed up
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
including current control file in backup set
channel ORA_DISK_1: starting piece 1 at 28-DEC-14
channel ORA_DISK_1: finished piece 1 at 28-DEC-14
piece handle=/tmp/rman_bkp/stnd_backp_0dpr8v12_1_1.bak tag=TAG20141228T025048 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 28-DEC-14
We took the backup inside /tmp/rman_bkp directory and ensure that it contains nothing besides the incremental backups of scn.
Step 4: Take the standby controlfile backup of the Primary database controlfile.
At primary database:
RMAN> backup current controlfile for standby format ‘/tmp/rman_bkp/stnd_%U.ctl’;
Starting backup at 28-DEC-14
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
including standby control file in backup set
channel ORA_DISK_1: starting piece 1 at 28-DEC-14
channel ORA_DISK_1: finished piece 1 at 28-DEC-14
piece handle=/tmp/rman_bkp/stnd_0epr8v4e_1_1.ctl tag=TAG20141228T025301 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 28-DEC-14
Starting Control File and SPFILE Autobackup at 28-DEC-14
piece handle=/u01/app/oracle/flash_recovery_area/PRIM/autobackup/2014_12_28/o1_mf_s_867466384_b9y8sr8k_.bkp comment=NONE
Finished Control File and SPFILE Autobackup at 28-DEC-14
Step 5: Transfer the backups from the Primary cluster to the Standby cluster.
[oracle@cluster1 ~]$ cd /tmp/rman_bkp/
[oracle@cluster1 rman_bkp]$ ls -ltrh
total 24M
-rw-r—–. 1 oracle oinstall 4.2M Dec 28 02:51 stnd_backp_0cpr8v08_1_1.bak
-rw-r—–. 1 oracle oinstall 9.7M Dec 28 02:51 stnd_backp_0dpr8v12_1_1.bak
-rw-r—–. 1 oracle oinstall 9.7M Dec 28 02:53 stnd_0epr8v4e_1_1.ctl
oracle@cluster1 rman_bkp]$ scp *.* oracle@cluster2:/tmp/rman_bkp/
oracle@cluster2’s password:
stnd_0epr8v4e_1_1.ctl 100% 9856KB 9.6MB/s 00:00
stnd_backp_0cpr8v08_1_1.bak 100% 4296KB 4.2MB/s 00:00
stnd_backp_0dpr8v12_1_1.bak 100% 9856KB 9.6MB/s 00:00
Step 6: On the standby cluster, connect the Standby Database through RMAN and catalog the copied
incremental backups so that the Controlfile of the Standby Database would be aware of these
incremental backups.
At standby database:-
SQL>
[oracle@cluster2 ~]$ rman target /
RMAN> catalog start with ‘/tmp/rman_bkp’;
using target database control file instead of recovery catalog
searching for all files that match the pattern /tmp/rman_bkp
List of Files Unknown to the Database
=====================================
File Name: /tmp/rman_bkp/stnd_0epr8v4e_1_1.ctl
File Name: /tmp/rman_bkp/stnd_backp_0dpr8v12_1_1.bak
File Name: /tmp/rman_bkp/stnd_backp_0cpr8v08_1_1.bak
Do you really want to catalog the above files (enter YES or NO)? yes
cataloging files…
cataloging done
List of Cataloged Files
=======================
File Name: /tmp/rman_bkp/stnd_0epr8v4e_1_1.ctl
File Name: /tmp/rman_bkp/stnd_backp_0dpr8v12_1_1.bak
File Name: /tmp/rman_bkp/stnd_backp_0cpr8v08_1_1.bak
Step 7. Shutdown the database and open it in mount stage for recovery purpose.
SQL> shut immediate;
SQL> startup mount;
Step 8.Now recover the database :-
RMAN> rman target /
RMAN> recover database noredo;
Starting recover at 28-DEC-14
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=25 device type=DISK
channel ORA_DISK_1: starting incremental datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
destination for restore of datafile 00001: /u01/app/oracle/oradata/stand/system01.dbf
destination for restore of datafile 00002: /u01/app/oracle/oradata/stand/sysaux01.dbf
destination for restore of datafile 00003: /u01/app/oracle/oradata/stand/undotbs01.dbf
destination for restore of datafile 00004: /u01/app/oracle/oradata/stand/users01.dbf
destination for restore of datafile 00005: /u01/app/oracle/oradata/stand/example01.dbf
channel ORA_DISK_1: reading from backup piece /tmp/rman_bkp/stnd_backp_0cpr8v08_1_1.bak
channel ORA_DISK_1: piece handle=/tmp/rman_bkp/stnd_backp_0cpr8v08_1_1.bak tag=TAG20141228T025048
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:03
Finished recover at 28-DEC-14
exit.
Step 9 : Shutdown the physical standby database, start it in nomount stage and restore the standby controlfile
backup that we had taken from the primary database.
SQL> shut immediate;
SQL> startup nomount;
[oracle@cluster2 rman_bkp]$ rman target /
RMAN> restore standby controlfile from ‘/tmp/rman_bkp/stnd_0epr8v4e_1_1.ctl’;
ecovery Manager: Release 11.2.0.1.0 – Production on Sun Dec 28 03:08:45 2014
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
connected to target database: PRIM (not mounted)
RMAN> restore standby controlfile from ‘/tmp/rman_bkp/stnd_0epr8v4e_1_1.ctl’;
Starting restore at 28-DEC-14
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=20 device type=DISK
channel ORA_DISK_1: restoring control file
channel ORA_DISK_1: restore complete, elapsed time: 00:00:01
output file name=/u01/app/oracle/oradata/stand/stand.ctl
output file name=/u01/app/oracle/flash_recovery_area/stand/stand.ctl
Finished restore at 28-DEC-14
Step 10: Shutdown the standby database and mount the standby database, so that the standby database would
be mounted with the new controlfile that was restored in the previous step.
SQL> shut immediate;
SQL> startup mount;
At standby database:-
SQL> alter database recover managed standby database disconnect from session;
At primary database:-
SQL> select thread#,max(sequence#) from v$archived_log group by thread#;
THREAD# MAX(SEQUENCE#)
———- ————–
1 215
At standby database:-
SQL> select thread#,max(sequence#) from v$archived_log group by thread#;
THREAD# MAX(SEQUENCE#)
———- ————–
1 215
Step 11.Now we will cancel the recovery to open the database
SQL> alter database recover managed standby database cancel;
SQL> alter database open;
Database altered.
SQL> alter database recover managed standby database using current logfile disconnect from session;
Database altered.
SQL> select open_mode from v$database;
OPEN_MODE
——————–
READ ONLY WITH APPLY
Now standby database is in sync with the Primary Database.
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