10g RMAN compression ratio

Just use RMAN backup to compressed backup for a 10.2 standard edition database.

The db total size (exclude redo, controlfile, temp) is 18850MB.
The total used size of tablespaces is 10550MB.
The RMAN compressed backupset size is 2329MB.

From above figure,  for the default compress algorithm, the compression ration ranges from 4.53 (10550/2329) to 8.09 (18850/2329). This is quite good number to me, which can help to save lots of space to keep backupset file.