Here I am presenting the simple steps
to demonstrate how to take incremental level backup,perform restore and
recovery using RMAN.One can learn Rman incremental level backup easily
by going through this post. I used oracle 10g express edition.
Difference between differential and cumulative incremental backup will be clear by going through this simple demo.
Simple scenarios has been taken.
Demonstrating DIFFERENTIAL INCREMENTAL BACKUP
1. Database is in NOARCHIVELOG mode.
2. Not using recovery catalog.
3. RMAN configuration setting that I used is following. I am posting the output of
RMAN> SHOW ALL;
using target database control file instead of recovery catalog
RMAN configuration parameters are:
CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
CONFIGURE BACKUP OPTIMIZATION ON;
CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
CONFIGURE CONTROLFILE AUTOBACKUP ON;
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '/usr/lib/oracle/xe/backup/cf_%F';
CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE CHANNEL DEVICE TYPE DISK MAXPIECESIZE 400 M FORMAT '/usr/lib/oracle/xe/backup/df_%U';
CONFIGURE MAXSETSIZE TO UNLIMITED; # default
CONFIGURE ENCRYPTION FOR DATABASE OFF; # default
CONFIGURE ENCRYPTION ALGORITHM 'AES128'; # default
CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/dbs/snapcf_XE.f'; # default
4.
Since database is in NOARCHIVELOG mode, it is necessary to shut down
the database cleanly using immediate,normal or transactional options.
RMAN> shutdown
5. To take incremental 0 level backup,mount the database. This step is required even in non-incremental backups.
RMAN> startup mount
6. Issue
RMAN> BACKUP INCREMENTAL LEVEL 0 DATABASE TAG 'FULL_INC';
This takes the full backup of the database and also includes controlfile as well as spfile.
7. Issue
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS
---------- ---------- ---------- ---------- ---------- --- ----------------
FIRST_CHANGE# FIRST_TIM
------------- ---------
1 1 0 52428800 1 YES UNUSED
0
2 1 1 52428800 1 NO CURRENT
1077758 08-MAR-11
SQL> select checkpoint_change# from v$database;
CHECKPOINT_CHANGE#
------------------
1084366
8. RMAN> ALTER DATABASE OPEN;
9. Now, perform some DML operations. For example,
SQL> CREATE TABLE T1(C1 NUMBER);
SQL> INSERT INTO T1 VALUES(10);
SQL> /
SQL> /
SQL> COMMIT;
10. Again, shutdown the database to take incremental level backup.
RMAN>SHUTDOWN
RMAN>STARTUP MOUNT
RMAN> BACKUP INCREMENTAL LEVEL 1 DATABASE TAG 'INC_1';
It backups only the changes made since the last incremental level n or lower backup.
11. Open the database again to perform some insertions.
RMAN> ALTER DATABASE OPEN;
12. SQL> INSERT INTO T1 VALUES(1);
SQL> /
SQL> /
SQL> /
SQL> COMMIT;
13. Shutdown the database again to take incremental level 2 backup.
RMAN> SHUTDOWN
RMAN> STARTUP MOUNT
RMAN> BACKUP INCREMENTAL LEVEL 2 DATABASE TAG 'INC_1';
14. Open database again to made some insertions.
RMAN> ALTER DATABASE OPEN;
SQL> INSERT INTO T1 VALUES(9);
SQL> /
SQL> /
SQL> COMMI;
15. select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS
---------- ---------- ---------- ---------- ---------- --- ----------------
FIRST_CHANGE# FIRST_TIM
------------- ---------
1 1 0 52428800 1 YES UNUSED
0
2 1 1 52428800 1 NO CURRENT
1077758 08-MAR-11
SQL> select checkpoint_change# from v$database;
CHECKPOINT_CHANGE#
------------------
1084663
Here all the changes since the last backup has been stored in the redo logs.
16. Now, delete controlfile.
$ mv oradata/XE/controlfile cf.bak
17. RMAN> SHUTDOWN ABORT;
18. RMAN> STARTUP
Database will not open. Database will only go upto the NOMOUNT state since controlfile has been lost.
19. RMAN> Now following steps are needed to recover the database.
20. RMAN> SET CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '/usr/lib/oracle/xe/backup/cf_%F';
If controlfile autobackup is located in default location, then we can skip this step.
21. RMAN> RESTORE CONTROLFILE FROM AUTOBACKUP
22. RMAN> ALTER DATABASE MOUNT;
23. RMAN> RESTORE DATABASE;
It will restore the database using the 0 level backup.
24. RMAN> RECOVER DATABASE
Watch
the output carefully. You can recognise various backups that are being
applied. Look for the tags that you have given to backupsets. It will
applies all the incrementals one by one. First it will apply level 1
incremental, and then level 2. Then it will search for appropriate log
sequence and applies the same if found. If log switching has not been
taken place after the last incremental backup, then we get all the data
without any data loss. And database will restore upto the current point
in time. In our case no log switching has taken place and all the data
since the last backup exist in the redologs. NOREDO option is needed when log switching has taken place. NOREDO option is not needed if log switch has not taken place.
25.RMAN> ALTER DATABASE OPEN RESETLOGS;
26. Now, view the table t1 and you will find the table restored upto the latest point in time if all the redos has been applied.
27. Always take full backup of the database after opening the database in resetlogs mode.
Demonstrating CUMULATIVE INCREMENTAL BACKUP
Here we will utilize same scenario as above,i.e. no recovery catalog mode,no archivelog mode.
We will start here by taking incremental level 0 backup.
1. RMAN> SHUTDOWN
2. RMAN> STARTUP MOUNT
3. RMAN> BACKUP INCREMENTAL LEVEL 0 DATABASE TAG 'FULL_INC';
4. RMAN> ALTER DATABASE OPEN;
5. SQL> SELECT CHECKPOINT_CHANGE# FROM V$DATABASE;
6. Make some insertion.
SQL> INSERT INTO T1 VALUES(2);
SQL> /
SQL> /
SQL> COMMIT;
7.
Again shutdown the database to take incremental level 1 database which
will copies only the changed blocks since the last incremental level 0
backup.
RMAN> BACKUP INCREMENTAL LEVEL 1 DATABASE TAG 'INC_1';
8.ALTER DATABASE OPEN;
9. SQL> INSERT INTO T1 VALUES(3);
SQL> /
SQL> /
SQL> COMMIT;
10.
Again shutdown the database to take cumulative incremental level 1
backup, this time. This backups all the changes made after the last n-1
or lower backup,here it will backup all the changes since the
incremental level 0 backup.
RMAN> BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE TAG 'CUM_1';
11. RMAN> ALTER DATABASE OPEN;
12. Perform some DML again.
SQL> INSERT INTO T1 VALUES(9);
SQL>/
SQL> /
SQL> COMMIT;
13. Now, we will shutdown the database to take incremental level 1 backup this time.
RMAN> SHUTDOWN
RMAN> STARTUP MOUNT
RMAN> BACKUP INCREMENTAL LEVEL 1 DATABASE TAG 'INC_1_1';
14. RMAN> ALTER DATABASE OPEN;
15. SQL> INSERT INTO T1 VALUES(0);
SQL> /
SQL> COMMIT;
16. Delete controlfile.
$ mv oradata/XE/controlfile cf.bak
17. RMAN> SHUTDOWN ABORT
18. RMAN> STARTUP
Database will not open.It will go upto only NOMOUNT state.
19. RMAN> SET CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '/usr/lib/oracle/XE/backup/cf_%F';
20. RMAN> RESTORE CONTROLFILE FROM AUTOBACKUP;
21. RMAN> ALTER DATABASE MOUNT;
22. RMAN> RESTORE DATABASE;,
It will restore the database from the last incremental level 0 database.
23. RMAN> RECOVER DATABASE;
Here
NOREDO option is not necessary as it is assumed that redo logs has not
been switched and complete recovery is possible. Check the same by
looking at the contents of v$log and comparing with the
checkpoint_change# that have noted in step 5. If all the changes since
that value exist in the redo logs then NOREDO option is not needed. Else
it is required.
Here first of all, cumulative incremental level 1
backup would restore as there is no need for the backup having tag
'INC_1' as cumulative incremental level 1 backup take backup of all the
changes since the last level 0 backup. Thus our first incremental level 1
backup is not applied. Then it applies backup having tag 'INC_1_1'
which we take after cumulative incremental level backup. After that it
will apply all the changes recorded in the online redologs.
Thus ,
only two incremental level backups needed to apply here. But in the
first scenario all the incremental backups had been applied. Thus we can
say that using cumulative incremental
backup in your incremental strategy provides faster recovery as number
of incremental backups to be applied is less.
24. RMAN> ALTER DATBASE OPEN RESETLOGS;
25. Take whole database backup after opening database in resetlogs mode. It is a good practice to perform th same.
26. Now check your table. It must have all the changes that we made, keeping all the scenario same.
If multiple channels are allocated for the backup, then this query
will return multiple records. Each record will be indicating the status
of individual channel
