RMAN Backup Compression Types
Oracle introduced RMAN backup compression from 10g version onward. From 11g version, Oracle introduced 4 different types of backup compression methods.
Both Oracle 11g and 12c has below 4 types of compression types
BASIC: Its the basic compression method which is default configured in rman parameters.
LOW: Lead compression method where DB performance and backup size hold good.
MEDIUM: Recommended method as its the best combination of DB performance and compression ratio.
HIGH: You get the highest backup compression but DB performance and backup will be very slow.
Note: except BASIC compression, you need an advance compression license to use LOW, MEDIUM and HIGH compression types.
Check compression type
Inside RMAN parameters, we have compression algorithm type which defines the type of compression method to be used. You can check it via below command.
Note: default compression set to BASIC does not mean that every backup that you trigger will be compressed.
The backup compression algorithm will only be used when you use BACKUP AS COMPRESSED clause while taking the backups.
Change compression type
If you have the advance compression license, then you can always change to other types of compression methods available
RMAN> CONFIGURE COMPRESSION ALGORITHM ‘HIGH’; RMAN> backup as compressed backupset database plus archivelog;
You can always change compression algorithm to Low, Medium and High.
Testing backup compression
When you use backup compression, you must know what are the benefits of it and when to use the particular type of backup compression method.
In a test case, we tested backup compression on a small database and below are our findings:
Note: the backup size and time might differ based on channels, server and other factors.