Which two are true about backup set compression using RMAN default compression? (Choose two.)
Which two are true about backup set compression using RMAN default compression? (Choose two.)
Backup set compression using RMAN default compression adds CPU overhead to backup operations due to the binary compression process. Compression can only be done for locally managed tablespaces, as Oracle has recommended using locally managed tablespaces over dictionary managed tablespaces since Oracle 10g for better efficiency and ease of management.
It's BE. Why E? Oracle strongly recommends the use of locally managed tablespaces instead of dictionary managed tablespaces as of 10g. And it you do have dictionary managed tablespaces) then you should ideally covert it/them to locally managed tablespace(s) for ease of use and management.
B, E You may try and succeed : backup as compressed backupset device type disk database section size 100m; (not A, not D). If they speak about Unused block compression then : RMAN skips reading, and backing up, any database blocks that are not currently allocated to some database object. This is regardless of whether those blocks had previously been allocated (bellow HWM). (Not C) data file has to be locally managed. (E)
I fully agree with what mporislav said
I believe that the options chosen should be B and C. Based on the following reference it is clear that blocks below the watermark are not included in the backup and that there is CPU overhead in the backup operations with compression. https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-backup-concepts.html#GUID-50F8DBCD-C285-491F-B8E7-E1B2140E1B51
As documentation says "When employing unused block compression, RMAN skips reading, and backing up, any database blocks that are not currently allocated to some database object. This is regardless of whether those blocks had previously been allocated." so you are wrong unfortunetally.
A is not correct - compression can be used WITHOUT writing to media, just in VALID command also: backup as compressed backupset validate database; Starting backup at 21-MAY-21 ... B is CORRECT C is not correct - it is introduced in 10g unused block compression D is not correct - checked in practice zillion times E - is correct only for introduced in 10g unused block compression, anyway it is correct ... so I would go with B and E
ORA 12913- Cannot create dictionary managed tablespace
I agree with BE
https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-backup-concepts.html#GUID-073C85A4-E28C-4FE2-A089-1EABF3D00070
Agree with B, but didn't find any information about section size and locally managed tablespace.
I think BD