Many people ask about RMAN best practices for very large databases, and there are many factors to consider. 

Choosing the backup software

Choose wisely between RMAN and hardware-level backups - Many hardware vendors offer disk-level backup & recovery that has some advantages over an Oracle-centric approach.

Many shops choose RMAN as the backbone of their backup and recovery strategy.  You can configure RMAN to maintain your backup strategy and RMAN will create the backups, and purge old backups automatically. When you need to restore a file, RMAN will use the catalogue to locate the backup, restore the file (or data blocks) and recover the database. RMAN is intelligent enough to determine what needs to be restored and recovered and execute the appropriate actions, and RMAN excels in environments with multiple Oracle databases.

Factors in an Oracle backup & recovery strategy

Most multi-terabyte Oracle shops have the goals of maximizing safety while minimizing disk storage and recovery time:

• Recoverability time for backup - RMAN has a wealth of backup options (full, incremental, block level), and you must choose the method that results in the fastest recoverability for your shop.   

• Validity of backup - I always do a media check on my backups storage media, and some clients want to duplex their backup sets at a remote site.  If you can afford it, a disk-to-disk backup is very fast and more reliable media than tape. 

• Speed of backup - You can maximize your backup time by dedicating backup devices one-for-one with the physical disk spindles.  This ensures that a backup of any size can be done in as long as it tales to backup one spindle.

See my related notes on RMAN Oracle backup strategies: