Example—Daily Cumulative, Weekly Cumulative Backup Schedule

Table 23–7 shows the most commonly used incremental backup schedule. This schedule is recommended for most situations. With this schedule, the following occurs:

• Each day, all files that have changed since the lower-level backup at the end of the previous week are saved.

• For each weekday level 9 backup, the previous level 0 or level 5 backup is the closest backup at a lower level. Therefore, each weekday tape contains all the files that changed since the end of the previous week or the initial level 0 backup for the first week.

• For each Friday level 5 backup, the closest lower-level backup is the level 0 backup done at the beginning of the month. Therefore, each Friday's tape contains all the files changed during the month up to that point.

Table 23–7 Daily Cumulative/Weekly Cumulative Backup Schedule

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

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

Table 23–8 Contents of Tapes for Daily Cumulative/Weekly Cumulative 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	a b c d e f g h i j k

Tape Requirements for the Daily Cumulative, Weekly Cumulative 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

• The most recent Friday tape

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