Below are the most effective techniques used by Oracle DBAs to speed up RMAN backups.

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1. Increase RMAN Channels (Parallelism)

RMAN uses channels as streams for reading data files and writing backup pieces. Increasing the number of channels enables parallel backup operations, significantly improving throughput.

Example:

CONFIGURE DEVICE TYPE DISK PARALLELISM 4;

Or manually allocate channels:

RUN {
  ALLOCATE CHANNEL ch1 DEVICE TYPE DISK;
  ALLOCATE CHANNEL ch2 DEVICE TYPE DISK;
  ALLOCATE CHANNEL ch3 DEVICE TYPE DISK;
  BACKUP DATABASE;
}

Impact:
More channels allow multiple datafiles to be backed up simultaneously.

Important consideration:

• Do not exceed the I/O capacity of the storage system.

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2. Use Section Size (Multisection Backups)

For very large datafiles, RMAN can split the file into multiple sections so multiple channels can process different parts of the same file simultaneously.

Example:

BACKUP DATABASE SECTION SIZE 1G;

Benefit

• Large datafiles are backed up in parallel
• Dramatically improves backup speed for multi-terabyte databases.

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3. Enable Backup Compression

Compression reduces the amount of data written to disk or transferred across the network.

Example:

CONFIGURE COMPRESSION ALGORITHM 'MEDIUM';
CONFIGURE DEVICE TYPE DISK BACKUP TYPE TO COMPRESSED BACKUPSET;

Benefits:

• Reduced disk I/O
• Faster backup for storage-limited systems

Trade-off:

• Increased CPU utilization

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4. Backup as Backupset Instead of Image Copy

RMAN supports two formats:

• Image copies
• Backup sets

Backup sets are usually faster because unused blocks are skipped.

Example:

BACKUP AS BACKUPSET DATABASE;

Benefit

• Reduces backup size
• Improves performance.

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5. Enable Block Change Tracking (For Incremental Backups)

When performing incremental backups, enabling Block Change Tracking prevents RMAN from scanning the entire database.

Example:

ALTER DATABASE ENABLE BLOCK CHANGE TRACKING;

Benefit:

• Incremental backups become significantly faster.

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6. Optimize Backup Strategy

Instead of always running full backups, use incremental backups.

Example strategy:

• Weekly Level 0 backup
• Daily Level 1 incremental backups

Example:

BACKUP INCREMENTAL LEVEL 1 DATABASE;

Benefit:

• Smaller backup window
• Reduced I/O

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7. Use Faster Storage for Backup Destination

Backup performance is often limited by write speed.

Common improvements:

• Write backups to high-speed disk
• Avoid slow network mounts
• Use dedicated backup storage

For example:

• Backup to local disk first
• Later copy to tape

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8. Enable RMAN Multiplexing

RMAN can read multiple files simultaneously into a single backup set.

Example configuration:

CONFIGURE FILESPERSET 4;

Benefit:

• Better I/O utilization

But excessive multiplexing may reduce restore performance.

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9. Optimize Archive Log Backups

Archivelogs can accumulate and slow backups.

Best practice:

BACKUP ARCHIVELOG ALL DELETE INPUT;

This ensures:

• Logs are backed up once
• Deleted after backup

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10. Tune I/O Throughput

Check whether the system is I/O bound.

Monitor:

• V$BACKUP_ASYNC_IO
• V$IOSTAT_FILE
• OS tools (iostat, sar)

Possible improvements:

• Increase disk throughput
• Separate backup disks from database disks
• Use ASM striping

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11. Offload Backups to Standby Database

In environments using **Oracle Data Guard, backups can be taken from the standby database.

Example:

Run RMAN on standby:

BACKUP DATABASE;

Benefit:

• Offloads backup workload from primary database.

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12. Use Incremental Merge Strategy

For very large databases, incremental merge allows maintaining an updated image copy using incremental backups.

Example:

BACKUP INCREMENTAL LEVEL 1 FOR RECOVER OF COPY DATABASE;

Benefit:

• Near-zero recovery time
• Faster backups