I have a policy with 6 schedules, one for each day of the week except 
Sunday, each one does a full backup with a 2 week retention. The purpose 
for these backups is disaster recovery.

However if a user wants to restore a file that was deleted 3 months ago, 
we are in trouble. For this reason I want to start some sort of long 
term backup. As the data is quite static I decided long term incremental 
backups would use the least amount of tapes. For instance, a cumulative 
incremental each Sunday with a 12 month retention. Initially I would 
need a full set of tapes, but for each subsequent week I would only need 
1 or maybe 2 tapes.

I have tried this and it did not work as I expected:

01. Monday,     Full
02. Tuesday,    Full
03. Wednesday,  Full
04. Thursday,   Full
05. Friday,     Full
06. Saturday,   Full
07. Sunday,     Incremental
08. Monday,     Full
09. Tuesday,    Full
10. Wednesday,  Full
11. Thursday,   Full
12. Friday,     Full
13. Saturday,   Full
14. Sunday,     Incremental

After some testing I realised that backup number 14 was doing a 
cumulative incremental from the last full backup, which was backup 
number 13. I wanted it to do a cumulative incremental against the last 
cumulative incremental ie backup number 07. The problem with this is 
that a file created and backed-up during the week on Thursday will only 
be on tape with a 2 week retention, not the 12 month that I require.

The main reason I want cumulative incremental is to save tape cost, 52 
full sets of tapes will be megabucks. How do I go about solving this 
problem?

Regards
--
Tom