Hmm OK we need to clarify a few things as there are some correct answers and some incorrect ones in amongst this thread
1) The Append Period starts when the BKF file is first created (or when it is overwritten). Once this period has started it does not move (so the end date/time does not change) no matter how many appends are written into the same file. (Sorry pkh but one of your answers was therefore slightly wrong because of this)
2) The Overwrite Protection period starts at the end of the last job to write data into the BKF file. As such as you run more append jobs this period will move and reset itself so that the end of this period is always based on the tinme of the last data write + the overwrite protection setting.
3) If you set a 32 day append period and a 1 Day overwrite (as mentioned in the first post) then assuming your append backups do all run for 32 days, the BKF file will become overwritable 33days + The time taken for your last differential job. So if you are not careful on the 33rd day a new BKF file will be created and the existing one will become overwritable a couple of hours or so later - but then not actually get used until another job needs overwritable media (which could be another 32 days away if you only run the described set of jobs)
4) If you set 32 day append and 1 day overwrite, but for some reason some of the later differential jobs don't run then the BKF file will be overwritable earlier (although will remain appendable as well)
5) Similarly if you set Append period to 32 days and overwrite protection to 32 days then assuming your differentials do all append for the first 32 days then it will be 64days + the time taken for the last job before it is overwritable. And yes a second BKF file would be created on the 33rd day.
6) because of points 3 and 5 you want to make the sum of the Append and Overwrite Protection settings to be and hour or two smaller than difference between the number of days between overwrites and how long your differential backup jobs run.
5) When an overwrite occurs - it overwrites the whole BKF file it's doesn't start with overwriting the oldest data - if you want to overwrite ONLY the oldest data you would have to reconsider your 1 BKF file plan and go back to 1 BKF file per day/job
6) We don't recommend appending to BKF/B2D destinations for ever as this creates an infinitely large media famiily which can cause catalog problems. Which is why we usually recommend starting all backup to disk jobs as overwrite and have separate BKF files. However you are not trying to append for ever you just want to append for 32 days - that said I would still be concerned about your plan as if you let Backup Exec make one BKF file for each backup and one file is corrupted then you will only lose one day's data however if you have it all write to one BKF file and that file corrupts then you lose everything.
Unfortunately you don't say if your full backup will write to the same backup to disk folder or how long you keep your full backups for. You also don't say if other jobs run in the environment. This kind iof makes it difficult to answer you question fully. However I will make some assumptions to answer your orignal question. (Although like others I would not recommend your idea as a good solution)
Assumption 1 - Only the differential backup jobs write to this backup to Disk Folder, all other backups write to tape or to a different backup to disk folder
Assumption 2 - You want to overwrite the BKF file when the job starts on 33rd day
Accepting the above assumptions
- Set your media set to 32 days Append and 0 Hours (or maybe 12 Hours) Overwrite Protection. Note: The reason you can get away with 0 Hours is Assumption 1 - no other jobs write to the folder and becasue the job starts as an Append (below)
- Set your differential job to start as an Append with Overwrite if appendable media is not available and to use the above media set. (you need the Ovewrite option if no appendable to trigger the overwrite on 33rd day)
