RMAN BACKUP RESTORE RECOVERY

Incremental backups:

Backuping up database based on changed blocks 

stratergies:- incremental (differential(default) and cumulative )

incremental :- level 0 (full db) , level 1 ( backuping blocks since level 0 ) 

differential:- backuping db since last level 1 backup. 

cumulative:- backuping db since last level 0 backup. 

differential:- sun(level 0), mon (level 1) , tue(level 1), wed(level 1), thu(level 1), fri(level 1), sat(level 1)

cumulative:- sun(level 0), mon(sun+level 1), tue(sun+mon+level1), wed(sun+mon+tue+level1),

thu(sun+mon+tue+wed+level1), fri(sun+mon+tue+wed+thu+level1),sat(sun+mon+tue+wed+thu+fri+level1)

Recovery stepsfor both (differential & cumulative will be same rman auto-select backups):-

RMAN> STARTUP MOUNT;

RMAN> RESTORE DATABASE;

RMAN> RECOVER DATABASE;

RMAN> ALTER DATABASE OPEN RESETLOGS;

Side-by-Side Comparison

Factor	Differential	Cumulative
Backup size (daily)	Smaller (only daily changes)	Larger (grows each day)
Backup time	Faster	Slower (more blocks each day)
Storage usage	Less	More
Recovery time	Slower (apply multiple L1s)	Faster (apply only 1 L1)
Backup sets to restore	L0 + all L1s since L0	L0 + latest L1 only
Complexity	Slightly complex recovery	Simple recovery
Best for	Limited storage environments	Fast recovery requirement (low RTO)

 

Point-in-time-recovery:- 

1. Restore to specific time:-

RMAN> STARTUP MOUNT;

RMAN> RUN {
        SET UNTIL TIME "TO_DATE('2024-04-09 14:00:00','YYYY-MM-DD HH24:MI:SS')";
        RESTORE DATABASE;
        RECOVER DATABASE;
      }
RMAN> ALTER DATABASE OPEN RESETLOGS;

2. Restore to specific scn:-

RMAN> STARTUP MOUNT;

RMAN> RUN {

        SET UNTIL SCN 1234567;

        RESTORE DATABASE;

        RECOVER DATABASE;

      }

RMAN> ALTER DATABASE OPEN RESETLOGS;

3. Restore to specific log sequence:-

RMAN> STARTUP MOUNT;

RMAN> RUN {

        SET UNTIL SEQUENCE 500 THREAD 1;

        RESTORE DATABASE;

        RECOVER DATABASE;

      }

RMAN> ALTER DATABASE OPEN RESETLOGS;

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TABLESPACE RECOVERY:-

-- Take tablespace offline

SQL> ALTER TABLESPACE users OFFLINE IMMEDIATE;

-- Restore and recover tablespace

RMAN> RESTORE TABLESPACE users;

RMAN> RECOVER TABLESPACE users;

-- Bring tablespace online

SQL> ALTER TABLESPACE users ONLINE;

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Datafile recovery:-

-- If datafile is missing/corrupted

RMAN> RESTORE DATAFILE 5;

RMAN> RECOVER DATAFILE 5;

-- Or by filename

RMAN> RESTORE DATAFILE '/oradata/users01.dbf';

RMAN> RECOVER DATAFILE '/oradata/users01.dbf';

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Control file recovery:-

-- If controlfile is lost

RMAN> STARTUP NOMOUNT;

RMAN> RESTORE CONTROLFILE FROM AUTOBACKUP;

-- OR from specific location

RMAN> RESTORE CONTROLFILE FROM '/backup/ctrl_backup';

RMAN> ALTER DATABASE MOUNT;

RMAN> RECOVER DATABASE;

RMAN> ALTER DATABASE OPEN RESETLOGS;

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Archivelog only recovery (no restore required)

-- If datafiles are intact but archivelogs needed

RMAN> RECOVER DATABASE;          -- applies pending archivelogs

-- Recover using specific archivelog

RMAN> RECOVER DATABASE UNTIL SEQUENCE 450;

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