The Ora DBA: RMAN Backup Strategy: Full, Incremental and Archivelog Backups

Oracle DBA RMAN Backup and Recovery Incremental Backup ARCHIVELOG Oracle 19c

Oracle Recovery Manager (RMAN) supports several backup types: Full, Incremental Level 0, Level 1 Differential and Level 1 Cumulative. They look similar on the surface, but they behave very differently when RMAN builds a backup chain and, more importantly, when you need to restore.

This guide explains each backup type, the commands to run them, how they affect recovery, and the one-time settings that make any RMAN strategy faster and safer.

Note: All paths in this guide, such as /u01/backup/rman, are examples. Replace them with the backup location used in your environment.

Connect to RMAN

$ rman target /

Recommended One-Time Configuration

Configure these settings once. RMAN stores them in the control file and applies them to every backup.

RMAN> CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 7 DAYS;

RMAN> CONFIGURE CONTROLFILE AUTOBACKUP ON;

RMAN> CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK
      TO '/u01/backup/rman/AUTO_CTL_%F';

Setting	Why It Matters
Retention policy	Defines which backups are obsolete and can be deleted safely
Controlfile autobackup	Takes an extra copy of the control file and SPFILE after every backup and structural change, in the same backup folder

To review the current configuration at any time:

RMAN> SHOW ALL;

How the Backup Scripts Are Built

Every backup script in this guide is complete and self-contained. Each one writes all of the following to the same folder, so a single directory holds everything needed for a restore:

Step in the Script	Purpose
`ARCHIVE LOG CURRENT` (before)	Archives the current redo so all redo up to the start of the backup is available
Database backup	Full, Level 0 or Level 1 backup of the datafiles
`ARCHIVE LOG CURRENT` (after)	Archives the redo generated during the backup, which is required to make the backup consistent
Archived log backup	Backs up every archived log not yet backed up, including those generated during the backup
Control file backup	Taken last, so it records every backup piece created by the script
SPFILE backup	Needed to start the instance when restoring to a new server

Note: SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT' works in every version from 11g onwards. From 12c, the SQL '...' wrapper is optional and ALTER SYSTEM ARCHIVE LOG CURRENT; can be run directly.

Full Backup

A Full backup copies all used blocks of the database. It is a standalone backup and is not part of the incremental backup strategy.

RUN {
    ALLOCATE CHANNEL c1 DEVICE TYPE DISK;
    ALLOCATE CHANNEL c2 DEVICE TYPE DISK;

    SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';

    BACKUP DATABASE
        FORMAT '/u01/backup/rman/FULL_%d_%T_%U.bkp'
        TAG 'FULL_BACKUP';

    SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';

    BACKUP ARCHIVELOG ALL NOT BACKED UP 1 TIMES
        FORMAT '/u01/backup/rman/ARCH_%d_%T_%U.bkp'
        TAG 'ARCHIVELOG';

    BACKUP CURRENT CONTROLFILE
        FORMAT '/u01/backup/rman/CTL_%d_%T_%U.bkp'
        TAG 'CONTROLFILE';

    BACKUP SPFILE
        FORMAT '/u01/backup/rman/SPFILE_%d_%T_%U.bkp'
        TAG 'SPFILE';

    RELEASE CHANNEL c1;
    RELEASE CHANNEL c2;
}

Incremental Level 0 Backup

A Level 0 backup also copies all used blocks, but it is recorded as the baseline for later Level 1 backups. Every incremental strategy starts with a Level 0.

RUN {
    ALLOCATE CHANNEL c1 DEVICE TYPE DISK;
    ALLOCATE CHANNEL c2 DEVICE TYPE DISK;

    SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';

    BACKUP INCREMENTAL LEVEL 0 DATABASE
        FORMAT '/u01/backup/rman/L0_%d_%T_%U.bkp'
        TAG 'LEVEL_0';

    SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';

    BACKUP ARCHIVELOG ALL NOT BACKED UP 1 TIMES
        FORMAT '/u01/backup/rman/ARCH_%d_%T_%U.bkp'
        TAG 'ARCHIVELOG';

    BACKUP CURRENT CONTROLFILE
        FORMAT '/u01/backup/rman/CTL_%d_%T_%U.bkp'
        TAG 'CONTROLFILE';

    BACKUP SPFILE
        FORMAT '/u01/backup/rman/SPFILE_%d_%T_%U.bkp'
        TAG 'SPFILE';

    RELEASE CHANNEL c1;
    RELEASE CHANNEL c2;
}

Full vs Level 0

Feature	Full Backup	Level 0 Backup
Command	`BACKUP DATABASE`	`BACKUP INCREMENTAL LEVEL 0 DATABASE`
Backs up all used blocks	Yes	Yes
Parent for Level 1 backups	No	Yes
Typical use	One-off backup before a change, clone or migration	Weekly baseline of an incremental strategy

Important: A Full backup cannot be the parent of a Level 1 backup. If you run a Level 1 when no Level 0 exists, RMAN automatically takes a Level 0 instead. This is why an "incremental" backup sometimes runs for hours after a Level 0 was deleted or never taken.

Level 1 Differential Backup

A differential Level 1 backs up the blocks changed since the most recent Level 0 or Level 1 backup. It is the default type of Level 1.

RUN {
    ALLOCATE CHANNEL c1 DEVICE TYPE DISK;
    ALLOCATE CHANNEL c2 DEVICE TYPE DISK;

    SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';

    BACKUP INCREMENTAL LEVEL 1 DATABASE
        FORMAT '/u01/backup/rman/L1_%d_%T_%U.bkp'
        TAG 'LEVEL_1_DIFF';

    SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';

    BACKUP ARCHIVELOG ALL NOT BACKED UP 1 TIMES
        FORMAT '/u01/backup/rman/ARCH_%d_%T_%U.bkp'
        TAG 'ARCHIVELOG';

    BACKUP CURRENT CONTROLFILE
        FORMAT '/u01/backup/rman/CTL_%d_%T_%U.bkp'
        TAG 'CONTROLFILE';

    BACKUP SPFILE
        FORMAT '/u01/backup/rman/SPFILE_%d_%T_%U.bkp'
        TAG 'SPFILE';

    RELEASE CHANNEL c1;
    RELEASE CHANNEL c2;
}

Sunday     Level 0
Monday     L1 Differential  →  changes since Sunday L0
Tuesday    L1 Differential  →  changes since Monday L1
Wednesday  L1 Differential  →  changes since Tuesday L1

Each backup contains only one day of changes, so daily backups stay small.

Level 1 Cumulative Backup

A cumulative Level 1 backs up all blocks changed since the most recent Level 0, using the CUMULATIVE keyword.

RUN {
    ALLOCATE CHANNEL c1 DEVICE TYPE DISK;
    ALLOCATE CHANNEL c2 DEVICE TYPE DISK;

    SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';

    BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE
        FORMAT '/u01/backup/rman/L1C_%d_%T_%U.bkp'
        TAG 'LEVEL_1_CUM';

    SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';

    BACKUP ARCHIVELOG ALL NOT BACKED UP 1 TIMES
        FORMAT '/u01/backup/rman/ARCH_%d_%T_%U.bkp'
        TAG 'ARCHIVELOG';

    BACKUP CURRENT CONTROLFILE
        FORMAT '/u01/backup/rman/CTL_%d_%T_%U.bkp'
        TAG 'CONTROLFILE';

    BACKUP SPFILE
        FORMAT '/u01/backup/rman/SPFILE_%d_%T_%U.bkp'
        TAG 'SPFILE';

    RELEASE CHANNEL c1;
    RELEASE CHANNEL c2;
}

Sunday     Level 0
Monday     L1 Cumulative  →  changes since Sunday L0
Tuesday    L1 Cumulative  →  changes since Sunday L0
Wednesday  L1 Cumulative  →  changes since Sunday L0

Each backup grows during the week, because it repeats all changes since the Level 0.

What Gets Restored? Differential vs Cumulative

The real difference appears during recovery. Assume the database fails on Wednesday after the Level 1 backup.

Differential strategy:
  Restore  Sunday L0
  Apply    Monday L1 + Tuesday L1 + Wednesday L1
  Apply    Archived logs after Wednesday L1

Cumulative strategy:
  Restore  Sunday L0
  Apply    Wednesday L1C only
  Apply    Archived logs after Wednesday L1C

Feature	Level 1 Differential	Level 1 Cumulative
Based on	Most recent Level 0 or Level 1	Most recent Level 0
Daily backup size	Smaller	Grows through the week
Needed for recovery	Level 0 + every Level 1 since + archived logs	Level 0 + latest Level 1 + archived logs
Recovery speed	Slower, more pieces to apply	Faster, fewer pieces to apply
Risk	One missing Level 1 breaks the chain	Fewer dependencies

Enable Block Change Tracking

Without Block Change Tracking, a Level 1 backup still reads every block in the database to find the changed ones. The backup is smaller, but not much faster. Block Change Tracking records changed blocks in a small file, so RMAN reads only those blocks.

SQL> ALTER DATABASE ENABLE BLOCK CHANGE TRACKING
     USING FILE '/u01/app/oracle/bct/PROD_bct.chg';

On ASM, specify the disk group instead:

SQL> ALTER DATABASE ENABLE BLOCK CHANGE TRACKING USING FILE '+DATA';

Verify that it is enabled:

SQL> SELECT STATUS, FILENAME FROM V$BLOCK_CHANGE_TRACKING;

Note: Block Change Tracking is available in Enterprise Edition. The first Level 1 after enabling it still reads all blocks; later Level 1 backups benefit fully.

Archived Log Backups Between Database Backups

In ARCHIVELOG mode, archived logs are what allow recovery from the last database backup to the point of failure. Every database backup script above already includes them. Between database backups, back up archived logs several times a day to limit data loss and free space in the archive destination. The control file is backed up last so it records the new pieces.

RUN {
    ALLOCATE CHANNEL c1 DEVICE TYPE DISK;
    ALLOCATE CHANNEL c2 DEVICE TYPE DISK;

    SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';

    BACKUP ARCHIVELOG ALL NOT BACKED UP 1 TIMES
        FORMAT '/u01/backup/rman/ARCH_%d_%T_%U.bkp'
        TAG 'ARCHIVELOG';

    BACKUP CURRENT CONTROLFILE
        FORMAT '/u01/backup/rman/CTL_%d_%T_%U.bkp'
        TAG 'CONTROLFILE';

    RELEASE CHANNEL c1;
    RELEASE CHANNEL c2;
}

Back Up and Delete Archived Logs

To remove archived logs from the archive destination once they are safely backed up:

RUN {
    ALLOCATE CHANNEL c1 DEVICE TYPE DISK;
    ALLOCATE CHANNEL c2 DEVICE TYPE DISK;

    SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';

    BACKUP ARCHIVELOG ALL NOT BACKED UP 1 TIMES
        FORMAT '/u01/backup/rman/ARCH_%d_%T_%U.bkp'
        TAG 'ARCHIVELOG'
        DELETE INPUT;

    BACKUP CURRENT CONTROLFILE
        FORMAT '/u01/backup/rman/CTL_%d_%T_%U.bkp'
        TAG 'CONTROLFILE';

    RELEASE CHANNEL c1;
    RELEASE CHANNEL c2;
}

Data Guard Warning: DELETE INPUT can remove archived logs that the standby has not applied yet. On a Data Guard primary, set a deletion policy first so RMAN never deletes unapplied logs:

RMAN> CONFIGURE ARCHIVELOG DELETION POLICY TO APPLIED ON ALL STANDBY;

Also note that DELETE INPUT removes logs from one archive destination only. Use DELETE ALL INPUT to remove them from all local destinations.

NOARCHIVELOG Mode

In NOARCHIVELOG mode, the backup must be consistent, so the database is shut down cleanly and mounted before the backup.

RMAN> SHUTDOWN IMMEDIATE;
RMAN> STARTUP MOUNT;

RUN {
    ALLOCATE CHANNEL c1 DEVICE TYPE DISK;
    ALLOCATE CHANNEL c2 DEVICE TYPE DISK;

    BACKUP INCREMENTAL LEVEL 0 DATABASE
        FORMAT '/u01/backup/rman/L0_%d_%T_%U.bkp'
        TAG 'LEVEL_0_NOARCH';

    BACKUP CURRENT CONTROLFILE
        FORMAT '/u01/backup/rman/CTL_%d_%T_%U.bkp'
        TAG 'CONTROLFILE';

    BACKUP SPFILE
        FORMAT '/u01/backup/rman/SPFILE_%d_%T_%U.bkp'
        TAG 'SPFILE';

    RELEASE CHANNEL c1;
    RELEASE CHANNEL c2;
}

RMAN> ALTER DATABASE OPEN;

Note: There is no archived log backup in this script because a NOARCHIVELOG database does not generate archived logs. Replace BACKUP INCREMENTAL LEVEL 0 DATABASE with BACKUP DATABASE for a Full backup.

Important: A NOARCHIVELOG database can only be restored to the time of a backup. Every change made after the last backup is lost. Use NOARCHIVELOG mode only for databases where that is acceptable, such as test environments.

Recommended Weekly Strategy

Many production sites combine both Level 1 types: differential backups keep daily backups small, while a mid-week cumulative backup shortens the recovery chain.

Day	Backup
Sunday	Level 0 + archived logs
Monday	Level 1 Differential + archived logs
Tuesday	Level 1 Differential + archived logs
Wednesday	Level 1 Cumulative + archived logs
Thursday	Level 1 Differential + archived logs
Friday	Level 1 Differential + archived logs
Saturday	Level 1 Differential + archived logs
Every few hours	Archived logs only

With this schedule, a failure on Saturday needs at most the Level 0, the Wednesday cumulative and three differential backups.

Housekeeping

Run these regularly to keep the RMAN repository in sync with the files on disk and to remove backups that are no longer needed:

RMAN> CROSSCHECK BACKUP;
RMAN> CROSSCHECK ARCHIVELOG ALL;

RMAN> DELETE NOPROMPT EXPIRED BACKUP;
RMAN> DELETE NOPROMPT OBSOLETE;

Note: EXPIRED means RMAN could not find the backup piece on disk. OBSOLETE means the backup is no longer needed under the retention policy.

Verify and Validate Backups

List the backups that exist:

RMAN> LIST BACKUP SUMMARY;

Check which files do not meet the retention policy:

RMAN> REPORT NEED BACKUP;

Most importantly, test that the backups can actually be restored, without restoring anything:

RMAN> RESTORE DATABASE PREVIEW;
RMAN> RESTORE DATABASE VALIDATE;

PREVIEW shows which backup pieces a restore would use. VALIDATE reads those pieces and checks them for corruption.

Tip: To check backup job status every morning without opening RMAN logs, see Step 13 of Oracle Database Daily Health Check.

Quick Reference

Backup Type	Command	Contains
Full	`BACKUP DATABASE`	All used blocks, standalone
Level 0	`BACKUP INCREMENTAL LEVEL 0 DATABASE`	All used blocks, baseline for Level 1
L1 Differential	`BACKUP INCREMENTAL LEVEL 1 DATABASE`	Changes since last Level 0 or Level 1
L1 Cumulative	`BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE`	Changes since last Level 0
Archived logs	`BACKUP ARCHIVELOG ALL`	Redo needed to recover to any point in time

Summary

A Full backup and a Level 0 backup contain the same blocks, but only Level 0 can be the parent of incremental backups. Differential Level 1 backups keep daily backups small, while cumulative Level 1 backups keep the recovery chain short. In ARCHIVELOG mode, archived log backups are what turn those backups into point-in-time recovery.

Back up the database, archived logs, control file and SPFILE together in one folder, enable controlfile autobackup and Block Change Tracking, set a retention policy, protect standby archives with a deletion policy, and validate your backups regularly. The right backup strategy is the one that meets your recovery time, not the one with the smallest backup size.

Key Takeaway: Design the backup strategy around the restore. A backup that has never been validated is only an assumption.

The Ora DBA

Monday, October 12, 2026

RMAN Backup Strategy: Full, Incremental and Archivelog Backups