Incremental Backup

[Mariel Gonzales Faylona]

I Just wanted to ask something about on Backup and recovery. In Incremental backup, what usually do we backup? What specific file do we backup?Is it redo log files or database files?

[Steven E. Protter · Accepted solution]

Sounds like you are using oracle.

If you do an incremental backup you should back up data,index,and control files at the very least.

If you want to be able to recover the database and roll transactions forward, get the archive log files and redo areas as well.

Note that fbackup can not get usable backups of open database files. Tools like netbackup and DP 5.x from HP can get good hot backups without bringing the database down.

SEP

[Indira Aramandla]

Hi Mariel,

Incremental backups

These are backups that are taken on blocks that have been modified since the last backup. These are useful as they don't take up as much space and time.

There are two kinds of incremental backups
Cumulative and Non cumulative.

Cumulative incremental backups include all blocks that were changed since the last backup at a lower level. This one reduces the work during restoration as only one backup contains all the changed blocks.

Noncumulative only includes blocks that were changed since the previous backup
at the same or lower level.
Using rman, you issue the command "backup incremental level n"

Attached is a note from Metalink Note:94114.1 that describes in detail the various scenarios of backup and recovery on Oracle.


Indira A

[Yogeeraj_1]

hi,

From the RMAN guide:


Incremental Backups

An incremental backup reads the entire file and then backs up only those data blocks that have changed since a previous backup. Oracle allows you to create and restore incremental backups of datafiles, tablespaces, or the whole database. Note that RMAN can include a control file in an incremental backup set, but the control file is always included in its entirety?no blocks are skipped.

The primary reasons for making an incremental backup are:

o To save tape when using a media manager.
o To save network bandwidth when backing up over a network.
o When the aggregate tape bandwidth available for tape write I/Os is much less than the aggregate disk bandwidth for disk read I/Os.
o To be able to recover changes to objects created with the NOLOGGING option.

If none of these criteria apply, then full backups are usually preferable because the application of the incremental backup increases recovery time while the cost savings is negligible.


You should know that an INCREMENTAL backup takes longer then a FULL backup -- it just reduces time to recover (less archives to roll forward through). It consumes less storage than a full backup would as well.

A typical scenario would be:
Sunday -- Full backup
Monday -- Incremental backup
Tuesday -- FAILURE

To recover:
a. restore sunday
b. apply monday incremental
c. roll forward through logs

As for the files you will be backing up, it will depend on the strategy adopted.

For instance, if you are doing a hot backup, it does not make sense to backup the data files.

RMAN helps a lot in identifying the required files to be backup and required for a restore ultimately...


hope this helps!

regards
yogeeraj