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This article mainly explains "whether RMAN chooses to compress the backup set". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn whether RMAN chooses to compress the backup set.

1. Overview of compressed backup

After Oracle 10g, the BACKUP command in RMAN adds an option for AS COMPRESSED BACKUPSET, and the backup set applies a compression algorithm during the creation process.

two。 Create a compressed backup

RMAN > backup as compressed backupset tablespace users

Then create an uncompressed backup of the same tablespace

RMAN > backup tablespace users

Compare these two backups.

RMAN > list backup of tablespace users

List of Backup Sets

=

BS Key Type LV Size Device Type Elapsed Time Completion Time

3 Full 1.34M DISK 00:00:00 22-OCT-18

BP Key: 3 Status: AVAILABLE Compressed: YES Tag: TAG20181022T012508

Piece Name: / u01/app/oracle/fast_recovery_area/ORCL/backupset/2018_10_22/o1_mf_nnndf_TAG20181022T012508_fwtqsnh9_.bkp

List of Datafiles in backup set 3

File LV Type Ckp SCN Ckp Time Name

4 Full 1012468 22-OCT-18 / u01/app/oracle/oradata/orcl/users01.dbf

BS Key Type LV Size Device Type Elapsed Time Completion Time

4 Full 8.31M DISK 00:00:00 22-OCT-18

BP Key: 4 Status: AVAILABLE Compressed: NO Tag: TAG20181022T012533

Piece Name: / u01/app/oracle/fast_recovery_area/ORCL/backupset/2018_10_22/o1_mf_nnndf_TAG20181022T012533_fwtqtfcp_.bkp

List of Datafiles in backup set 4

File LV Type Ckp SCN Ckp Time Name

4 Full 1012512 22-OCT-18 / u01/app/oracle/oradata/orcl/users01.dbf

As can be seen from the above, the compression ratio is still very large.

3. Whether to compress the backup set

Compressing backups can save a lot of space, but it will certainly slow down the speed of backup and recovery. Therefore, it is recommended that if the space is large enough, do not compress the backup set. After all, the purpose of our backup is to restore, and everything should focus on recovery.

At this point, I believe you have a deeper understanding of "whether RMAN chooses to compress the backup set". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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