Rolling forward a standby database using RMAN incremental backup

 Rolling forward a standby database using RMAN incremental backup when primary and standby are in ASM filesystem [ID 836986.1]


This can be used when we lost archived log files to be applied in standby or there is a huge gap between primary & Standby.


STEPS:

1) On the standby database, stop the managed recovery process (MRP)

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;

2) On the STANDBY DATABASE, find the SCN which will be used for the incremental backup at the primary database:

SQL> SELECT CURRENT_SCN FROM V$DATABASE;

SQL> select min(fhscn) from x$kcvfh;

In ideal situation the above 2 queries will return the almost same SCN. However if there is huge difference its better to take backup using the SCN from second query (lesser SCN), as one of the datafile may be behind.

CURRENT_SCN
---------------------
3162298

3) In RMAN, connect to the PRIMARY database and create an incremental backup from the SCN derived in the previous step:

RMAN> run {
allocate channel c1 device type disk;
BACKUP INCREMENTAL FROM SCN 8435060423152 DATABASE FORMAT '/dbaworkspace/roll_fwd/ForStandby_%U' tag 'FORSTANDBY';
release channel c1;
}

4) Transfer all backup sets created on the primary system to the standby system.

scp /tmp/ForStandby_* standby:/tmp

RMAN> CATALOG START WITH '/tmp/ForStandby';

using target database control file instead of recovery catalog
searching for all files that match the pattern /tmp/ForStandby

List of Files Unknown to the Database
=====================================
File Name: /tmp/ForStandby_2lkglss4_1_1
File Name: /tmp/ForStandby_2mkglst8_1_1

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/ForStandby_2lkglss4_1_1
File Name: /tmp/ForStandby_2mkglst8_1_1

5) Recover the STANDBY database with the cataloged incremental backup:

RMAN> RECOVER DATABASE NOREDO;

starting recover at 03-JUN-09
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=28 devtype=DISK
channel ORA_DISK_1: starting incremental datafile backupset restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
destination for restore of datafile 00001: +DATA/mystd/datafile/system.297.688213333
destination for restore of datafile 00002: +DATA/mystd/datafile/undotbs1.268.688213335
destination for restore of datafile 00003: +DATA/mystd/datafile/sysaux.267.688213333
channel ORA_DISK_1: reading from backup piece /tmp/ForStandby_2lkglss4_1_1
channel ORA_DISK_1: restored backup piece 1
piece handle=/tmp/ForStandby_2lkglss4_1_1 tag=FORSTANDBY
channel ORA_DISK_1: restore complete, elapsed time: 00:00:02
Finished recover at 03-JUN-09

6) In RMAN, connect to the PRIMARY database and create a standby control file backup:

RMAN> BACKUP CURRENT CONTROLFILE FOR STANDBY FORMAT '/tmp/ForStandbyCTRL.bck';

7) Copy the standby control file backup to the STANDBY system. 

scp /tmp/ForStandbyCTRL.bck standby:/tmp

8) We now need to refresh the standby controlfile from primary controlfile (for standby) backup. However, since the datafile names are likely different than primary, let's save the name of datafiles on standby first, which we can refer after restoring controlfile from primary backup to verify if any discrepancy. So, run below query from Standby and save results for further use.

set lines 200
col name format a60
select file#, name from v$datafile order by file# ;

9) From RMAN, connect to STANDBY database and restore the standby control file:

RMAN> SHUTDOWN;
RMAN> STARTUP NOMOUNT;
RMAN> RESTORE STANDBY CONTROLFILE FROM '/tmp/ForStandbyCTRL.bck';

Starting restore at 03-JUN-09
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=36 devtype=DISK

channel ORA_DISK_1: restoring control file
channel ORA_DISK_1: restore complete, elapsed time: 00:00:07
output filename=+DATA/mystd/controlfile/current.257.688583989
Finished restore at 03-JUN-09

10) Shut down the STANDBY database and startup mount:

RMAN> SHUTDOWN;

RMAN> STARTUP MOUNT;

11) Since the controlfile is restored from PRIMARY the datafile locations in STANDBY controlfile will be same as PRIMARY database, so catalog datafiles in STANDBY will do the necessary rename operations.

Perform the below step  in STANDBY for each diskgroup where the datafile directory structure between primary and standby are different.

RMAN> CATALOG START WITH '+DATA/mystd/datafile/';

List of Files Unknown to the Database
=====================================
File Name: +data/mystd/DATAFILE/SYSTEM.309.685535773
File Name: +data/mystd/DATAFILE/SYSAUX.301.685535773
File Name: +data/mystd/DATAFILE/UNDOTBS1.302.685535775
File Name: +data/mystd/DATAFILE/SYSTEM.297.688213333
File Name: +data/mystd/DATAFILE/SYSAUX.267.688213333
File Name: +data/mystd/DATAFILE/UNDOTBS1.268.688213335

Do you really want to catalog the above files (enter YES or NO)? YES
cataloging files...
cataloging done

List of Cataloged Files
=======================

File Name: +data/mystd/DATAFILE/SYSTEM.297.688213333
File Name: +data/mystd/DATAFILE/SYSAUX.267.688213333
File Name: +data/mystd/DATAFILE/UNDOTBS1.268.688213335

If any datafiles have been added to Primary AFTER scn 3162298 they will also have to be restored to the standby host and cataloged as shown above before doing the switch.
 To determine if any files have been added to Primary since the standby current scn:

SQL>SELECT FILE#, NAME FROM V$DATAFILE WHERE CREATION_CHANGE# > 3162298

RMAN> SWITCH DATABASE TO COPY;

datafile 1 switched to datafile copy "+DATA/mystd/datafile/system.297.688213333"
datafile 2 switched to datafile copy "+DATA/mystd/datafile/undotbs1.268.688213335"
datafile 3 switched to datafile copy "+DATA/mystd/datafile/sysaux.267.688213333"

Note:

At this point, you can compare the query output from step 8) for any discrepancy (other than newly added datafiles)  by running the same query as in Step 8) to ensure we have all the datafiles added in standby.

12) If the STANDBY database needs to be configured for FLASHBACK use the below step to enable.

SQL> ALTER DATABASE FLASHBACK OFF; 
SQL> ALTER DATABASE FLASHBACK ON;

13) On standby database, clear all standby redo log groups:

SQL> ALTER DATABASE CLEAR LOGFILE GROUP 1;
SQL> ALTER DATABASE CLEAR LOGFILE GROUP 2;
SQL> ALTER DATABASE CLEAR LOGFILE GROUP 3;
....

14) On the STANDBY database, start the MRP

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT;