RMAN Compressed Backup : Learn to reduce the size of Oracle Database Backups

Enhancements for RMAN Compressed Backup in different releases.

Rman compressed backup feature is been enhanced in version 10g onwards. In this article we will see the enhancements.

Oracle 10g

 RMAN Compressed backup feature is  available from Oracle 10g version .

Oracle 11g and 12c

Enhanced Compression Algorithm

From Oracle 11g onwards . RMAN supports 4 compression algorithm

BASIC :  Basic Compression : Advanced Compression License is not required

LOW    :  Least compression . Performance of database and backup is good . Advanced Compression License  required

HIGH   : Highest Compression.  Performance of database and backup is low. Advanced Compression License  required

MEDIUM:  Recommended . Good Combination of Compression Ratio and Performance . Advanced Compression License  required

Precompression Block Processing

Helps in finding the block suitable for binary compression. Consolidates free space in each block and setting that free space into binary zeroes.

The OPTIMIZE FOR LOAD option controls precompression processing. By specifying the default, OPTIMIZE FOR LOAD TRUE, you ensure that RMAN optimizes CPU usage and avoids precompression block processing. By OPTIMIZE FOR LOAD FALSE, RMAN uses additional CPU resources to perform precompression block processing.

RMAN Compressed Backup Command

Oracle 10g

RMAN > BACKUP AS COMPRESSED BACKUPSET DATABASE PLUS ARCHIVELOG;

Oracle 11g/12c

Without Advanced Compression

RMAN > CONFIGURE COMPRESSION ALGORITHM ‘BASIC’;

RMAN >  BACKUP AS COMPRESSED BACKUPSET DATABASE PLUS ARCHIVELOG;

With Advanced Compression

RMAN > CONFIGURE COMPRESSION ALGORITHM ‘HIGH’;

RMAN >  BACKUP AS COMPRESSED BACKUPSET DATABASE PLUS ARCHIVELOG;

As mentioned earlier , with Advanced Compression can be ‘HIGH’ , ‘MEDIUM’ or ‘LOW’.

Configure Precompression Block Processing.

RMAN >  OPTIMIZE FOR LOAD FALSE

If we configure OPTIMIZE FOR LOAD TRUE , which is the default value , RMAN will not perform precompression block processing .

Test Case For RMAN Compressed Backup

I have performed the following test case  to validate RMAN Compressed Backup. I took the backup of my test database , with and without RMAN compressed backup . Here is the results

Compression AlgorithmSize of Compressed BackupTime Taken
No900 MB( Un compressed) 2 Minutes
BASIC280 MB3.5 Minutes
HIGH210 MB7 Minutes
MEDIUM240 MB4.5 Minutes

 

This test results may be varying for you. But from these results we can confirm that , RMAN Compressed backup can reduce the size of backups upto 50 to 60% .

 

We recommend you to test this feature and share your feedback .

Happy Learning

Wysheid Team

 

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