Yes, I do keep an eye on our media and cycle "old" TSM tapes.  We have about
300 tapes onsite, 400 offsite.

Because TSM expires data based on policy and not on tape cycles, you do have
the possibility of getting a few tapes that are very old.  Because, as you
said, the first backup from a client tends to be a large chunk, most of
which does not change.

Now "old" is a relative term that is going to depend a lot on your
situation.

I don't want any of our tapes to be more than 2 years old.  Not because I
worry about having media older than that, but because of microcode levels.
We started with 3490 drives, which were no problem because it was a stable
technology.  But then we went to DLT for a short while, then STK9840's.  For
both DLT and 9840's, the drive microcode gets upgraded 2-4 times a year.

I don't want to be in the position of trying to read a tape that is 10
generations of microcode older than my drives  -  nothing good can come of
that, and it's easy to prevent.

Now in practice I find I rarely have to cycle any tapes manually.  Most of
the tapes recycle naturally, anyway, and many of our clients don't exist
more than 3 years because the hardware gets upgraded so frequently!

Anyway, I check on it about once a year.  Find maybe 5 tapes I decide to
move manually.  You could easily create a script to do it on a weekend.....


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Wanda Prather
The Johns Hopkins Applied Physics Lab
443-778-8769
wanda_prather AT jhuapl DOT edu

"Intelligence has much less practical application than you'd think" -
Scott Adams/Dilbert
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