Example—Daily Incremental, Weekly Cumulative Backups

The following table shows a schedule where each weekday tape contains only the files that changed since the previous day. In addition, each Friday's tape contains all files changed since the initial level 0 backup at the beginning of the month.

Table 46–11 Daily Incremental, Weekly Cumulative Backup Schedule

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

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

Table 46–12 Contents of Tapes for Daily Incremental, Weekly Cumulative Backup Schedule

	Mon	Tues	Wed	Thurs	Fri
Week 1	a b	c d	e f g	hi	a b c d e f g h i
Week 2	j k l	m	n o	p q	a b c d e f g h i j k l m n o p q r s

Tape Requirements for Daily Incremental, Weekly Cumulative Schedule

With this schedule, you need at least 9 tapes if you want to reuse daily tapes, which is not recommended. Preferably, you need 21 tapes if you save weekly tapes for a month: one tape for the level 0, four tapes for the Fridays, and four or 16 daily tapes.

• 1 tape for the level 0 backup.

• 4 tapes for all the Friday backups.

• 4 or 16 daily tapes.

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

• The level 0 tape.

• The most recent Friday tape.

• All the daily tapes since the last Friday tape, if any.