Configuring and Backing Up Oracle Databases Using RMAN - OCP: Oracle Database 12c Administrator Certified Professional - page 128

The hidden Talents of Compression
Sometimes a product feature has hidden benefits Compression is one of these. While
compression can help reduce the size of your backup sets, there is another potential
feature that we look at in the real world, and that is an overall reduction in I/O. With com-
pression enabled, we often see a reduction in backup and recovery times since there is
less disk I/O associated with the backup. This can result in reduced backup times, and the
backups may have less impact on the overall system.
Everything comes with a price, though, and in this case it's CPU. Compression comes
with a high CPU cost. On systems where there was plenty of CPU to go around, we have
seen compression significantly reduce backup times and I/O impacts.
Encryption
You can choose to encrypt your backups in Oracle Database 12 c . Several encryption options
are available to you, and they can be found by querying the V$RMAN_ENCRYPTION_ALGORITHMS
view. You can use the CONFIGURE command to define the default level of encryption that you
want to use. You then use the CONFIGURE command to enable encryption for the entire data-
base or for specific tablespaces.
For example, if you wanted to configure encryption for the entire database, you would
use the following commands:
RMAN> configure encryption algorithm "AES128";
RMAN> configure encryption for database on;
Encryption options for a given tablespace will take precedence over the database global
settings. Thus, you can enable global encryption for the database and disable it for a spe-
cific tablespace.
There are three different modes of encryption (as opposed to the algorithm used). These are
transparent mode, password-based encryption, and dual-mode encryption, which encompasses
both modes of encryption. For transparent encryption, you will need to create a wallet, and it
must be open. Transparent encryption will then occur automatically after you have issued the
CONFIGURE ENCRYPTION FOR DATABASE ON or CONFIGURE ENCRYPTION FOR TABLESPACE ON
command.
For password authentication, you will need to use the SET ENCRYPTION IDENTIFIED BY
command first to enable password-based authentication. If you are restoring, you will have to
use the SET DECRYPTION IDENTIFIED BY command to set the password to decrypt a backup.
You can also use the SET command to change the type of encryption for a specific backup or
to turn off encryption. Here is an example of the use of the SET ENCRYPTION command:
RMAN> set encryption identified by my_pass only on for all tablespaces;