Example—Daily Cumulative, Weekly Incremental Backups

The following table shows a schedule where each weekday tape accumulates all files that changed since the beginning of the week, or the initial level 0 backup for the first week. In addition, each Friday's tape contains all the files that changed that week.

Table 22–9 Daily Cumulative, Weekly Incremental Backup Schedule

	Floating	Mon	Tues	Wed	Thurs	Fri
1st of Month	0
Week 1		9	9	9	9	3
Week 2		9	9	9	9	4
Week 3		9	9	9	9	5
Week 4		9	9	9	9	6

The following table shows how the contents of the tapes can change across two weeks with the daily cumulative, weekly incremental backup schedule. Each letter represents a different file.

Table 22–10 Contents of Tapes for Daily Cumulative, Weekly Incremental Backup Schedule

	Mon	Tues	Wed	Thurs	Fri
Week 1	a b	a b c	a b c d	a b c d e	a b c d e f
Week 2	g	g h	g h i	g h i j	g h i j k

Tape Requirements for the Daily Cumulative, Weekly Incremental Backup Schedule

With this schedule, you need six tapes if you want to reuse daily tapes. However, you need nine tapes if you want to use four different daily tapes:

• One tape for the level 0 backup

• Four tapes for Fridays

• One or four daily tapes

If you need to restore a complete file system, you need the following tapes:

• The level 0 tape

• All the Friday tapes

• The most recent daily tape since the last Friday tape, if any