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Backup Methods

When defining your backup Media Sets, you need to decide on the backup method.

Backup methods use the
"Archive" attribute of a file:

Not Set (no checkmark):
This file is stored in exactly
the current version on a backup
media and has not been modified
since this backup.


Set (Checkmark placed):
This file is NOT in the current
version on a backup, because it
has either been created or modified
since the last backup.


By selecting/ not-selecting files based on the Archive attribute and by resetting / not-resetting
the Archive attribute, different backup methods can be implemented:

Select Files to
include in the backup:
Record backup of a
file in the Archive attribute:
Backup method :
select all files reset Full backup :
Makes a backup of all data-files and allows
to used other methods, like Incremental and/or
Differential backups.
select all files no reset Copy Data:
makes a backup of all data-files, but since the
Archive attribute does NOT record this
backup, it is not possible to used Incremental
and/or Differential backup methods.
select only files with
a Set Archive attribute
reset Incremental backup:
makes a backup of all data-files modified since
the last backup of this file
select only files with
a Set Archive attribute
no reset Differential Backup:
makes a backup of all file modified since
the last FULL backup of this file


The different methods are a compromise between the workload (=time) to make the backup
and the workload (=time) to recover data from the backup , called "Restore".

This can best be explained using examples:

1) Full backup on Fridays, Incremental backups on Monday to Thursday:
The Full backup on Friday will put all data on the backup media, which could take hours.
The Incremental backup's on Monday to Thursday will put only the data-files created or
modified since the last Incremental backup on the backup media:
- on Monday: the data created / modified since the FULL backup on Friday
- on Tuesday: the data created / modified since the Incremental backup on Monday
- on Wednesday: the data created / modified since the Incremental backup on Tuesday
- on Thursday: the data created / modified since the Incremental backup on Wednesday
Since usually only a small portion of the files on a disk are modified on one day, the Incremental
backup runs usually very quickly.

However, if you need to restore data, you need to restore the media of the last FULL Backup and
the media of ALL Incremental backups.

2) Full backup on Fridays, Differential backups on Monday to Thursday:
The Full backup on Friday will put all data on the backup media, which could take hours.
The Differential backup's on Monday to Thursday will put only the data-files created or
modified since the last FULL backup on the backup media:
- on Monday: the data created / modified since the FULL backup on Friday
- on Tuesday: the data created / modified since the FULL backup on Friday
- on Wednesday: the data created / modified since the FULL backup on Friday
- on Thursday: the data created / modified since the FULL backup on Friday
So, every day of the Differential backup, more and more data is put on the backup media.


If you need to restore data, you need to restore the media of the last FULL Backup and
the then only the media of LAST Differential backup.

See below the example of the Windows98 SE Backup-program offering the different methods
( = Types) of backup:

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