Whether using RMAN or a traditional
backup method, however, the database must be in ARCHIVELOG mode.
True incremental backups For any RMAN incremental backup, unchanged blocks since
the last backup will not be written to the backup file. This saves a significant amount of
disk space, I/O time, and CPU time. For restore and recovery operations, RMAN supports
incrementally updated backups. Data blocks from an incremental backup are applied
to a previous backup to potentially reduce the amount of time and number of files that
need to be accessed to perform a recovery operation. We will cover an example of an
incrementally updated backup later in this chapter.
Block-level recovery To potentially avoid downtime during a recovery operation, RMAN
supports block-level recovery for recovery operations that only need to restore or repair a
small number of blocks identified as being corrupt during the backup operation. The rest
of the tablespace and the objects within the tablespace can remain online while RMAN
repairs the damaged blocks. The rows of a table not being repaired by RMAN are even
available to applications and users.
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Chapter 12: Using Recovery Manager (RMAN) 421
Multiple I/O channels During a backup or recovery operation, RMAN can utilize many
I/O channels, via separate operating system processes, to perform concurrent I/O.
Traditional backup methods, such as a Unix cp command or an Oracle export, are
typically single-threaded operations.
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