这个新特性也有一些限制
- Compatible parameter must be set to 11.0 or higher
- Backup must use a disk or OSB channel
- For 'backup copy of <object>' or 'backup datafilecopy' the database must be open for undo optimization to be used.
- Not active for LEVEL 1 incremental backups, only for LEVEL 0 and FULL backups
MOS文档：RMAN 11G : RMAN UNDO backup optimization (文档 ID 406468.1)
A Complete Understanding of RMAN Compression (文档 ID 563427.1)