RAC Backup, Restore and Recovery using RMAN

RAC Backup, Restore and Recovery using RMAN

Following Example is for a 2-node Oracle RAC Cluster.

The logs are being archived to their respective node.

We are allocating channels to each node to enable the autolocate feature of RMAN in a RAC env.

1. Verify the databases are in archivelog mode and archive destination.

a. NODE 1: thread 1

SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            /u02/app/oracle/product/11.2.0/dbs/arch
Oldest online log sequence     20
Next log sequence to archive   21
Current log sequence           21

 b. NODE 2: thread 2

SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            /u02/app/oracle/product/11.2.0/dbs/arch
Oldest online log sequence     8
Next log sequence to archive   9
Current log sequence           9

2. Verify connectivity to the target nodes and catalog if used.

$ setenv TNS_ADMIN $ORACLE_HOME/network/admin
$ sqlplus /nolog
SQL> connect sys/pwd@node1 as sysdba
SQL> connect sys/pwd@node2 as sysdba
SQL> connect rman/rman@rcat

3. Set your testing areas.

Testing HOME for logs:  /u02/home/usupport/rman

Backups HOME Location:  /rman/V112

4. Connect using RMAN to verify and set the controlfile persistent configuration. 

The controlfiles are shared between the instances so configuring the controlfile on node 1 also sets it for all nodes in the RAC cluster.

* Always note the target DBID
    connected to target database: V112 (DBID=228033884)

*  Default Configuration

RMAN> SHOW ALL;
    CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
    CONFIGURE BACKUP OPTIMIZATION OFF; # default
    CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
    CONFIGURE CONTROLFILE AUTOBACKUP ON;
    CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '%F'; # default
    CONFIGURE DEVICE TYPE DISK PARALLELISM 1; # default
    CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
    CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
    CONFIGURE MAXSETSIZE TO UNLIMITED; # default
    CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u02/app/oracle/product/11.2.0/dbs/snapcf_V11201.f'; # default

*Configuring Channels to Use a Specific Node

To configure one RMAN channel for each policy-managed Oracle RAC database instance, use the following syntax:

CONFIGURE CHANNEL DEVICE TYPE disk CONNECT 'SYS/RAC@NODE1';'
CONFIGURE CHANNEL DEVICE TYPE disk CONNECT ''SYS/RAC@NODE2';

 5. Make a backup using the new persistent configuration parameters.

*  Backup database with differential incremental 0 and then archived logs   using the delete input option.

BACKUP INCREMENTAL LEVEL 0 FORMAT '/rman/V112/%d_LVL0_%T_%u_s%s_p%p' DATABASE;
BACKUP ARCHIVELOG ALL FORMAT '/rman/V112/%d_AL_%T_%u_s%s_p%p'DELETE INPUT;

* Backup again using differential incremental level 1

     BACKUP INCREMENTAL LEVEL 1 FORMAT '/rman/V112/%d_LVL1_%T_%u_s%s_p%p' DATABASE;

     BACKUP ARCHIVELOG ALL FORMAT '/rman/V112/%d_AL_%T_%u_s%s_p%p' DELETE INPUT;

* To simplify this you can also use PLUS ARCHIVELOG 

BACKUP INCREMENTAL LEVEL 0 FORMAT '/rman/V112/%d_LVL0_%T_%u_s%s_p%p'
DATABASE PLUS ARCHIVELOG FORMAT '/rman/V112/%d_AL_%T_%u_s%s_p%p' DELETE INPUT;

 This uses a different algorithm than backup database and backup archivelog in separate commands, the algorithm for PLUS ARCHIVELOG is:

     1. Archive log current
     2. Backup archived logs
     3. Backup database level 0
     4. Archive log current
     5. Backup any remaining archived log created during backup

6. Backupset maintenance using the configured retention policy

RMAN> LIST BACKUP SUMMARY;
RMAN> LIST BACKUP BY DATAFILE;
RMAN> LIST BACKUP OF DATABASE;
RMAN> LIST BACKUP OF ARCHIVELOG ALL;
RMAN> LIST BACKUP OF CONTROLFILE;

These above can be enhanced with the "until time" clause as well as the archivelog backups using "not backed up x times" to cut down on  many copies of a log in several backup sets.
Then continuing with SMR  Server Managed Recovery use the change archivelog from...until...delete  to remove old logs no longer needed on disk.

To check/delete obsolete backups  or archivelogs we use:

RMAN> REPORT OBSOLETE;

RMAN> DELETE OBSOLETE;
         or
RMAN> DELETE NOPROMPT OBSOLETE;

To check the database files:

RMAN> REPORT SCHEMA; 

7. Restore and Recover

Complete Recovery

With the database mounted on the node1 and no-mount on node2 connect to the target and catalog using RMAN.

      rman target / catalog rman/rman@rcat

    This script will restore and recover the database completely and open the database in read/write mode.  

run {
         RESTORE DATABASE;
         RECOVER DATABASE;
         ALTER DATABASE OPEN;
}

Incomplete Recovery

If you are using instance registration the database must be mounted to register with the listener. This means you must use the current controlfile for restore and recovery or setup a dedicated listener if not  already done. RMAN requires a dedicated server connection and does not work with using instance registration before mounting the controlfile.  Using the autobackup controlfile feature requires the DBID of the  TARGET database. It must be set when the database is not mounted and only the controlfile and spfile (from 9.2) can be restored this way.

    1.Shutdown node1 and node2

    2. Startup no-mount node2 and node1

    3.Start rman and restore the controlfile from autobackup:

     rman trace reco1.log

RMAN> CONNECT CATALOG rman/rman@rcat

RMAN> SET DBID=228033884;

RMAN> CONNECT TARGET

RMAN>  restore controlfile;

   4. If no catalog is used, you can restore the controlfile from autobackup

     % rman trace recocf.log

RMAN> SET DBID=228033884;

RMAN> CONNECT TARGET /

RMAN> RUN
{

 SET CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE disk TO '/rman/V112/%F';
       ALLOCATE CHANNEL d1 DEVICE TYPE disk;
       RESTORE CONTROLFILE FROM AUTOBACKUP
       MAXSEQ 5           # start at sequence 5 and count down (optional)
       MAXDAYS 5;         # start at UNTIL TIME and search back 5 days (optional)
       MOUNT DATABASE;
}

  5. Verify what is available for incomplete recovery.

    We will recover with the highest available redo information.  In a RAC database, both thread must be considered to determine highest available redo.  The options are "until time", "until scn", or "until sequence".  We will use the log sequence in this case.

   a.  First we need to find the highest sequence of each thread:

SQL> select max(sequence#) from v$archived_log L, v$database D

            where L.resetlogs_change# = D.resetlogs_change# and 

            thread#=1;

       MAX(SEQUENCE#)
       --------------
               25

SQL> select max(sequence#) from v$archived_log L, v$database D

            where L.resetlogs_change# = D.resetlogs_change# and 

            thread#=2;

       MAX(SEQUENCE#)
       --------------
             13

  b.  Next is to find the thread with lowest NEXT_CHANGE# scn.

SQL> select sequence#, thread#, first_change#, next_change#
             from v$archived_log L, v$database D
             where L.resetlogs_change# = D.resetlogs_change# and
             sequence# in (13,25);

      SEQUENCE#    THREAD# FIRST_CHANGE# NEXT_CHANGE#
     -------------------- -------------- ------------------------- -------------------------
                            25            1                           1744432                    1744802
                            13            2                           1744429                    1744805

SQL> select sequence#, thread#, first_change#, next_change#
           from v$backup_redolog
           where sequence# in (13,25);

      SEQUENCE#    THREAD# FIRST_CHANGE# NEXT_CHANGE#
      -------------------- -------------- ------------------------- -------------------------
                            25            1                           1744432                    1744802
                            13            2                           1744429                    1744805

In this case the next_change# SCN in thread 1 sequence 25 is lower than sequence 13 thread 2.  In a RAC environment, we use the lower to ensure we have the redo required from BOTH threads.   In other words, we use the lower (thread# 1) to ensure that ALL scn (s) in thread #1 exist in the available sequence for thread #2.

So we will set sequence 26 for thread 1 for RMAN  'until sequence'  recovery,  because RMAN stops the recovery  before applying the indicated sequence. Log sequence for  recovery  needs always  be sequence+1 to end  at +1 after applying the prior sequence.  I.e.:

       SET UNTIL SEQUENCE 26 THREAD 1;

6.  Get the command to add TEMPFILES after opening DB.

Locally Managed Temporary Tablespaces are not restored by  RESTORE command, we need to create them manually after recovery is complete.

If using LMT Temporary tablespace the controlfile will have the syntax  to add the tempfile after recovery is complete. The following command will give us the create controlfile statement:

               SQL> alter database backup controlfile to trace;

                Example:

      # Commands to add tempfiles to temporary tablespaces.
      # Online tempfiles have complete space information.
      # Other tempfiles may require adjustment.
        ALTER TABLESPACE TEMP ADD TEMPFILE '/dev/db/temp_01.dbf'  SIZE 41943040  REUSE AUTOEXTEND OFF;
      # End of tempfile additions.
      #

NOTE:  In newer versions, the tempfiles are added automatically. 

7. Run the rman script

Since log sequence 13 thread 2 next_change# is 3 changes ahead of thread 1 sequence 25 we are using sequence 26 (25+1) to stop recovery. This will restore  the data files and recover them applying all of sequence #25 of thread 1 and stopping at sequence #26. 

run {
       SET UNTIL SEQUENCE 26 THREAD 1;
       RESTORE DATABASE;
       RECOVER DATABASE;
       ALTER DATABASE OPEN RESETLOGS;
      }

 8. Review and understand the impact of resetlogs on the catalog.

After resetlogs a new incarnation for the database is recorded in the RMAN catalog and database controlfile.  Only one incarnation can be current and any need to restore from a previous incarnation requires you to "reset database to incarnation...". 

For example:

RMAN> LIST INCARNATION OF DATABASE V112;

List of Database Incarnations
DB Key  Inc Key  DB Name  DB ID            CUR  Reset SCN  Reset Time
-----------  ----------- ------------ ----------------  ------- --------------  ---------------
2656          2657       V112         228033884      NO   1                   29-MAY-13
2656          3132       V112         228033884      YES  1744806       13-JUN-13

We see that an "open resetlogs" was executed against this database on 13-JUN-2013. 

9. RMAN Sample Commands

* With a dedicated listener (not using instance registration)  restoring the controlfile.

 run {
 ALLOCATE CHANNEL D1 TYPE DISK CONNECT 'SYS/RAC@NODE1';
 ALLOCATE CHANNEL D2 TYPE DISK CONNECT 'SYS/RAC@NODE2';
  SET UNTIL SEQUENCE 14 THREAD 2;
   RESTORE CONTROLFILE;
  ALTER DATABASE MOUNT;
 RELEASE CHANNEL D1;
 RELEASE CHANNEL D2;
 }

 * Backup Archivelog

 BACKUP ARCHIVELOG ALL NOT BACKED UP 3 TIMES;
 BACKUP ARCHIVELOG UNTIL TIME 'SYSDATE-2' NOT BACKED UP 2 TIMES;