There would be scenarios where the standby database lags far behind from the primary database leading to Archive Gap. It could be due to one of the following reasons
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.
Oracle Database version : 11.2.0.1.0 My Oracle Database is using ASM.
Primary database : sspm Standby database : sssb
Primary Host : dev Standby Host : uat
The maximum archivelog sequence generated on the Primary Database is 1005.
SQL> select status,instance_name,database_role from v$database,v$instance; STATUS INSTANCE_NAME DATABASE_ROLE ------------ ---------------- ---------------- OPEN sspm PRIMARY SQL> select thread#,max(sequence#) from v$archived_log group bythread#; THREAD# MAX(SEQUENCE#) ------- ---------------- 1 1005
On the standby database, the maximum archivelog sequence that is applied is sequence 865.
SQL> select status,instance_name,database_role from v$database,v$instance; STATUS INSTANCE_NAME DATABASE_ROLE ------------ ---------------- ---------------- MOUNTED sssb PHYSICAL STANDBY SQL> select thread#,max(sequence#) from v$archived_log where applied='YES' group by thread#; THREAD# MAX(SEQUENCE#) ------- ---------------- 1 865
The standby database is lagging behind the primary database by around 140 archives (1005 – 865).
When I investigated the alert log file of the Primary database to find out the reason for the logs not getting applied on the standby database, I got to see the below error message.
Sun Mar 25 15:40:23 2012 Errors in file /u01/app/oracle/diag/rdbms/sspm/sspm/trace/sspm_arc2_18816.trc: ORA-00308: cannot open archived log '+FRA/sspm/archivelog/2012_03_25/thread_1_seq_866.1117.778865785' ORA-17503: ksfdopn:2 Failed to open file +FRA/sspm/archivelog/2012_03_25/thread_1_seq_866.1117.778865785 ORA-15012: ASM file '+FRA/sspm/archivelog/2012_03_25/thread_1_seq_866.1117.778865785' does not exist
So the problem was here. The archivelog sequence 866 was missing and was unavailable at the FRA site. There were few more archives missing on the FRA and nor did I had the backup to restore them on the standby database. My option was to go with Roll Forwarding the Standby Database using Incremental Backups. Below are the steps on how to roll forward the physical standby database.
Step 1: Take a note of the Current SCN of the Physical Standby Database.
Standby Database:
SQL> select current_scn from v$database; CURRENT_SCN ----------- 991247
Note down the CURRENT_SCN value of the standby database (991247) to proceed further.
Step 2 : Cancel the Managed Recovery Process on the Standby database.
Standby Database:
SQL>alter database recover managed standby database cancel;
Step 3: On the Primary database, take the incremental SCN backup from the SCN that is currently recorded on the standby database (991247)
Connect to the primary database and take the incremental SCN backup.
Primary Database:
[oracle@dev ~]$ rman target sys/oracle@sspm Recovery Manager: Release 11.2.0.1.0 - Production on Sun Mar 2515:44:45 2012 Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved. connected to target database: SSPM (DBID=1624493265) RMAN> backup incremental from scn 991247 database format '/u02/bkp/stnd_backp_%U.bak'; Starting backup at 25-MAR-12 using target database control file instead of recovery catalog allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=39 device type=DISK backup will be obsolete on date 01-APR-12 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=+DATA_NEW/sspm/datafile/system.256.778803539 input datafile file number=00002 name=+DATA_NEW/sspm/datafile/sysaux.257.778803541 input datafile file number=00003 name=+DATA_NEW/sspm/datafile/undotbs1.258.778803541 input datafile file number=00004 name=+DATA_NEW/sspm/datafile/users.259.778803543 channel ORA_DISK_1: starting piece 1 at 25-MAR-12 channel ORA_DISK_1: finished piece 1 at 25-MAR-12 piece handle=/u02/bkp/stnd_backp_10n6p3nl_1_1.bak tag=TAG20120325T154639 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:45 using channel ORA_DISK_1 backup will be obsolete on date 01-APR-12 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 25-MAR-12 channel ORA_DISK_1: finished piece 1 at 25-MAR-12 piece handle=/u02/bkp/stnd_backp_11n6p3p4_1_1.bak tag=TAG20120325T154639 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03 Finished backup at 25-MAR-12
Step 4: Take the standby controlfile backup of the Primary database controlfile.
Connect to the Primary database and create the standby controlfile backup.
Primary Database :
RMAN> backup current controlfile for standby format '/u02/stnd_%U.ctl'; Starting backup at 25-MAR-12 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 25-MAR-12 channel ORA_DISK_1: finished piece 1 at 25-MAR-12 piece handle=/u02/stnd_12n6p3qt_1_1.ctl tag=TAG20120325T154845 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03 Finished backup at 25-MAR-12
Step 5: Transfer the backups from the Primary Server to the Standby Server.
Primary Database :
[oracle@dev bkp]$ pwd /u02/bkp [oracle@dev bkp]$ ls -lrt total 13576 -rw-r----- 1 oracle oinstall 540672 Mar 25 15:47 stnd_backp_10n6p3nl_1_1.bak -rw-r----- 1 oracle oinstall 13336576 Mar 25 15:47 stnd_backp_11n6p3p4_1_1.bak [oracle@dev bkp]$ scp stnd* uat:/u02/bkp oracle@uat's password: stnd_backp_10n6p3nl_1_1.bak 100% 528KB 528.0KB/s 00:00 stnd_backp_11n6p3p4_1_1.bak 100% 13MB 6.4MB/s 00:02 [oracle@dev bkp]$ cd /u02 [oracle@dev u02]$ ls -lrt stnd* -rw-r----- 1 oracle oinstall 13336576 Mar 25 15:48 stnd_12n6p3qt_1_1.ctl [oracle@dev u02]$ scp stnd* uat:/u02 oracle@uat's password: stnd_12n6p3qt_1_1.ctl 100% 13MB 12.7MB/s 00:01 [oracle@dev u02]$
Step 6: On the standby server, 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.
I had the incremental backuppieces copied to the location ‘/u02/bkp‘ on the standby server.
Standby Database:
[oracle@uat ~]$ rman target sys/mydbpwd@sssb Recovery Manager: Release 11.2.0.1.0 - Production on Sun Mar 2515:51:02 2012 Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved. connected to target database: SSPM (DBID=1624493265, not open) RMAN> catalog start with '/u02/bkp'; Starting implicit crosscheck backup at 25-MAR-12 using target database control file instead of recovery catalog allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=37 device type=DISK Crosschecked 15 objects Finished implicit crosscheck backup at 25-MAR-12 Starting implicit crosscheck copy at 25-MAR-12 using channel ORA_DISK_1 Crosschecked 2 objects Finished implicit crosscheck copy at 25-MAR-12 searching for all files in the recovery area cataloging files... File Name: +arch/SSSB/ARCHIVELOG/2012_03_25/thread_1_seq_200.453.778846881 File Name: +arch/SSSB/ARCHIVELOG/2012_03_25/thread_1_seq_201.454.778846881 File Name: +arch/SSSB/ARCHIVELOG/2012_03_25/thread_1_seq_202.455.778846881 File Name: +arch/SSSB/ARCHIVELOG/2012_03_25/thread_1_seq_203.456.778846881 File Name: +arch/SSSB/ARCHIVELOG/2012_03_25/thread_1_seq_137.457.778846881 File Name: +arch/SSSB/ARCHIVELOG/2012_03_25/thread_1_seq_204.458.778846881 File Name: +arch/SSSB/ARCHIVELOG/2012_03_25/thread_1_seq_205.459.778846883 File Name: +arch/SSSB/ARCHIVELOG/2012_03_25/thread_1_seq_856.947.778861691 File Name: +arch/SSSB/ARCHIVELOG/2012_03_25/thread_1_seq_858.949.778861709 File Name: +arch/SSSB/ARCHIVELOG/2012_03_25/thread_1_seq_857.950.778861719 searching for all files that match the pattern /u02/bkp List of Files Unknown to the Database ===================================== File Name: /u02/bkp/stnd_backp_10n6p3nl_1_1.bak File Name: /u02/bkp/stnd_backp_11n6p3p4_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: /u02/bkp/stnd_backp_10n6p3nl_1_1.bak File Name: /u02/bkp/stnd_backp_11n6p3p4_1_1.bak
Step 7: Recover the standby database with the cataloged incremental backup pieces.
RMAN> recover database noredo; Starting recover at 25-MAR-12 allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=32 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: +DATA/sssb/datafile/system.274.778865099 destination for restore of datafile 00002: +DATA/sssb/datafile/sysaux.275.778865193 destination for restore of datafile 00003: +DATA/sssb/datafile/undotbs1.276.778865259 destination for restore of datafile 00004: +DATA/sssb/datafile/users.277.778865273 channel ORA_DISK_1: reading from backup piece /u02/bkp/stnd_backp_10n6p3nl_1_1.bak channel ORA_DISK_1: piece handle=/u02/bkp/stnd_backp_10n6p3nl_1_1.bak tag=TAG20120325T154639 channel ORA_DISK_1: restored backup piece 1 channel ORA_DISK_1: restore complete, elapsed time: 00:00:01 Finished recover at 25-MAR-12
Step 8 : Shutdown the physical standby database, start it in nomount stage and restore the standby controlfile backup that we had taken from the primary database.
Standby Database:
RMAN> shutdown immediate database dismounted Oracle instance shut down RMAN> startup nomount connected to target database (not started) Oracle instance started Total System Global Area 659730432 bytes Fixed Size 2216264 bytes Variable Size 398462648 bytes Database Buffers 255852544 bytes Redo Buffers 3198976 bytes RMAN> restore standby controlfile from '/u02/stnd_12n6p3qt_1_1.ctl'; Starting restore at 25-MAR-12 allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=21 device type=DISK channel ORA_DISK_1: restoring control file channel ORA_DISK_1: restore complete, elapsed time: 00:00:04 output file name=+DATA/sssb/controlfile/current.273.778864875 Finished restore at 25-MAR-12
Step 9: 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.
Standby Database:
RMAN> <strong>shutdown immediate Oracle instance shut down RMAN> startup mount connected to target database (not started) Oracle instance started database mounted Total System Global Area 659730432 bytes Fixed Size 2216264 bytes Variable Size 398462648 bytes Database Buffers 255852544 bytes Redo Buffers 3198976 bytes
Step 10: If the datafile location of the primary and standby databases are different, then you need to follow this step. If not, then proceed with Step 11.
The datafiles of my primary database are residing on the Diskgroup +DATA_NEW on the primary server and the datafiles on the standby database are residing on the Diskgroup +DATA on the standby server, the datafiles location are different.
Since, I have restored the standby controlfile backuppiece of my primary database on the standby database (Step 7) and mounted the standby database, the standby database controlfile would now have the locations of the datafiles recorded as available in the Primary database. So, we need to make the standby controlfile understand that the datafiles location of the standby database are different from that of the Primary database. For this, you need to catalog the datafile location of the standby database to its controlfile as shown below.
Connect the standby database through RMAN and catalog the location of its datafiles and later switch them.
Standby Database:
RMAN> catalog start with '+DATA/SSSB/DATAFILE'; searching for all files that match the pattern +DATA/SSSB/DATAFILE List of Files Unknown to the Database ===================================== File Name: +data/SSSB/DATAFILE/SYSTEM.274.778865099 File Name: +data/SSSB/DATAFILE/SYSAUX.275.778865193 File Name: +data/SSSB/DATAFILE/UNDOTBS1.276.778865259 File Name: +data/SSSB/DATAFILE/USERS.277.778865273 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/SSSB/DATAFILE/SYSTEM.274.778865099 File Name: +data/SSSB/DATAFILE/SYSAUX.275.778865193 File Name: +data/SSSB/DATAFILE/UNDOTBS1.276.778865259 File Name: +data/SSSB/DATAFILE/USERS.277.778865273 RMAN> switch database to copy; datafile 1 switched to datafile copy "+DATA/sssb/datafile/system.274.778865099" datafile 2 switched to datafile copy "+DATA/sssb/datafile/sysaux.275.778865193" datafile 3 switched to datafile copy "+DATA/sssb/datafile/undotbs1.276.778865259" datafile 4 switched to datafile copy "+DATA/sssb/datafile/users.277.778865273" RMAN>
Step 11: If the datafile locations of the primary and the standby databases are same, then there is no necessity to perform the catalogging operation as done in the previous step.
On the standby database, start the Managed Recovery Process.
Standby Database:
SQL> alter database recover managed standby database disconnect from session; Database altered. SQL> select process,status,sequence# from v$managed_standby; PROCESS STATUS SEQUENCE# --------- ------------ ---------- ARCH CONNECTED 0 ARCH CONNECTED 0 ARCH CONNECTED 0 ARCH CONNECTED 0 RFS IDLE 0 RFS IDLE 0 RFS IDLE 1010 RFS IDLE 0 MRP0 WAIT_FOR_LOG 0 9 rows selected.
Step 12: On the Primary database, check the Maximum Archivelog Sequence generated.
Primary Database:
SQL> select thread#,max(sequence#) from v$archived_log group bythread#; THREAD# MAX(SEQUENCE#) ------- ---------------- 1 1009
Step 13: Check the maximum archivelog sequence that is applied on the Physical standby database.
SQL> select thread#,max(sequence#) from v$archived_log where applied='YES' group by thread#; THREAD# MAX(SEQUENCE#) ------- ---------------- 1 1009
So, here we can see from Steps 12 and 13 that the maximum archivelog sequence generated on the Primary database is sequence# 1009 and that applied on the Physical Standby Database is also 1009 which means that the Standby database is in sync with the Primary Database. You can check it out by generating an archive sequence on the Primary database and check if its shipped and applied on the standby database.
Primary Database:
SQL> alter system switch logfile; System altered. SQL> select thread#,max(sequence#) from v$archived_log group by thread#; THREAD# MAX(SEQUENCE#) ------- ---------------- 1 1010
Standby Database:
SQL> select thread#,max(sequence#) from v$archived_log where applied='YES' group by thread#; THREAD# MAX(SEQUENCE#) ------- ---------------- 1 1010
Now standby database is in sync with the Primary Database.
