1. Administrator's Guide
  2. Introduction to Recovery Appliance
  3. Traditional Database Backup Techniques
  4. Incremental Backups and RECOVER COPY

Incremental Backups and RECOVER COPY

The RMAN technique shown in Figure 1-2 makes daily incremental backups, and then uses the RECOVER COPY command to merge the incremental changes into the full database copy. In this way, the database copy on disk is "rolled forward" every day.

Figure 1-2 RECOVER COPY on Disk, and Backup to Tape

Description of Figure 1-2 follows
Description of "Figure 1-2 RECOVER COPY on Disk, and Backup to Tape"

This technique has the following advantages:

  • Only one initial full backup is required, which reduces the total weekly backup window time.

  • An RMAN SWITCH command can point the control file to the database copy, which turns the copy into an actual database file, and thus eliminates the RESTORE step.

Some disadvantages are as follows:

  • You must have sufficient disk space to keep a copy of the whole database on disk, and the archived redo log files required to recover it.

  • Only one physical copy of the database exists. You select the point in time at which to keep the copy, so you can recover to subsequent points in time. For example, to restore to any point in time within the past week, your physical copy must be older than SYSDATE-7. The disadvantages are:

    • You cannot recover to a time earlier than the time at which you maintain the database copy.

    • The closer your recovery point in time is to the current time, the more incremental backups you must restore and apply to the copy. This technique adds time to the overall recovery time objective.

  • The database copy cannot be compressed or encrypted.