RMAN versus EXPORT Incremental backups

PURPOSE
-------
The following documentation announces the obsolescence of the incremental exports:

1. "Oracle8i Utilities Release 2 (8.1.6)" (which is included as such in
   "Oracle Documentation Library, Release 8.1.7") says:

   Incremental, Cumulative, and Complete Exports

   Important: Incremental, cumulative, and complete Exports are obsolete
              features that will be phased out in a subsequent release.
              You should begin now to migrate to Oracle's Backup and
              Recovery Manager for database backups.

2. The Note 120608.1 "[8.1.7.0] Generic Server README for Oracle8i Release 3"
   says:

   5.2.3 Incremental, Cumulative, and Complete Features No Longer Supported
   Incremental, cumulative, and complete Exports are obsolete features.
   They are no longer documented, nor is their use supported by Oracle
   Corporation.

RMAN incremental backup is the only corresponding feature to replace the EXPORT
incremental backup.

This document describes the differences between both.

SCOPE & APPLICATION
-------------------

For those DBAs that use EXPORT incremental backups, the document illustrates
the points they should be aware of when migrating from EXPORT incremental backups
strategy towards RMAN incremental backups.


Comparable features between EXPORT / RMAN
-----------------------------------------


              EXPORT                 |             RMAN
________________________________________________________________________________

                            Levels of increment
________________________________________________________________________________

3 levels                             | 5 levels 0,1,2,3,4 and 2 types
INCTYPE=COMPLETE FULL=Y             |   Level 0 (equivalent)
         baseline for all cumulative | 
         and incremental backups     |
                                     |
INCTYPE=CUMULATIVE FULL=Y           | CUMULATIVE INCREMENTAL 
         backs up changes since last |   backs up all blocks changed since most
         cumulative or complete      |   recent level n-1 or lower
                                     |
INCTYPE=INCREMENTAL  FULL=Y         | DIFFERENTIAL INCREMENTAL
         backs up changes since last |   backs up all blocks changed since most
         incremental, cumulative or  |   recent level n or lower
         complete                    |  

* A higher number of levels in RMAN may reduce recovery time in case of media recovery.

________________________________________________________________________________

                             What is backed up ?
________________________________________________________________________________

If only one row of a table is changed| All blocks changed since the last
the ENTIRE table is backed up in the | backup  <=  level n (for differential)
next incremental export (of any type)| All blocks changed since the last
                                     | backup  <=  level n-1 (for culumative)                               

* The EXPORT incremental backup relies on object level and RMAN on block level.
* The amount of data to be backed up is optimized in RMAN.
________________________________________________________________________________
                                
                                Reporting
________________________________________________________________________________

To display the list of available     | To display the list of available
incremental backups and content:     | incremental backups:
                                     |
SELECT * FROM                        | RMAN> list backupset of database;
SYS.INCEXP                           | 
  List of tables exported in all     |      
  incremental exports                |       
SYS.FIL                              |
  all incremental/cumulative exports |
SYS.INCVID                           |
  ID of the last valid export, used  |
  to determine the ID of next export |
                                     | To report files requiring a new backup if
                                     | a complete recovery would need more than the
                                     | specified number of incremental:
                                     |
                                     | RMAN> report need backup incremental n
                                     |       database;

* With RMAN report command, the DBA can anticipate the need of new backups to
  reduce recovery time.

________________________________________________________________________________

                                  Usage
________________________________________________________________________________

1/ Recreation of a database and      | The incremental RMAN backup allows media
   incremental imports in case of a  | recovery at different levels:
   database erased                   |   * database
                                     |   * tablespace
2/ Recreation of a dropped table     |   * datafile
                                   
* RMAN automatically selects the successive incremental backups to be restored
  and applied during a media recovery.


RELATED DOCUMENTS
-----------------
Oracle Documentation Library, Release 8.1.7 Oracle8i Utilities Release 2 (8.1.6)
Note 120608.1  [8.1.7.0] Generic Server README for Oracle8i Release 3
Note 50875.1   Getting Started with Server-Managed Recovery (SMR) and RMAN
Note 115118.1  Using an incremental export to recover a dropped table