Beginning Oracle Database 11g Administration From Novice to Professional

CHAPTER 12 BACKUPS 261
Oracle-Managed Backups vs. User- Managed Backups
Backups created using Recovery Manager (RMAN) are called Oracle- managed backups
and backups created by other methods are called user- managed backups. For example,
Network Appliance provides an advanced technology that can be used to create snapshots
of the largest databases in seconds or minutes by recording only the addresses of
the blocks in the database instead of the data contained in the blocks—a copy of a block
is only made if the data in one of these blocks is subsequently changed.
Advantages of Oracle- Managed Backups
Backups created using Recovery Manager have many advantages:
database can be backed up with the simple words .
history data is needed during recovery operations, but it can be queried by the
database administrator at any time; a typical use is to verify that the database has
been backed up.
not available anywhere else. Examples
are incremental backups, detection of corrupted blocks, and recovery of single
blocks.
Advantages of User- Managed Backups
Some types of user- managed backups offer great advantages. For example, snapshot
technology has the advantage of lightning speed of both backup and recovery. Making
a backup of a file is lightning fast because it only requires that the addresses of blocks be
recorded, not the data contained in the blocks—recovery of a file is also lightning fast
because it only requires that one list of block addresses be switched with another. The
best of both worlds is achieved when snapshots are registered in the Recovery Manager
repository—this allows Recovery Manager to use the snapshots for database recovery.
Practical Demonstration: Physical Backups
Here is a practical demonstration of the use of RMAN to create a backup copy of the
database. As you will see, this can be accomplished with a few short commands. First we
give an appropriate value—it controls the format in which dates are displayed.
When we invoke RMAN, it displays version information and gives us a command
prompt: