... >Basically, he wants to know if there is any way that when the data expires it >becomes completely unusable/unrecoverable, even by someone with the >time/money/motivation to take a scratch tape and piece together what's on it.
By data processing definition, tapes - like disks or any other media (including paper) - are supposed to be physically secure, as in kept in a room that non-authorized people cannot enter, and that the people in the room are trustworthy. That is the fundamental protection for tapes written by any application. Expiration is a logical process, not physical: nothing goes near the tape in the process. Only the "catalog entry" for the expired data is obliterated, while the tape remains intact. Being an append-only medium, there is no potential for partial erasure of tape contents. You can wholly write over the tape with binary zeroes when it is empty if you like, to obliterate prior contents; but next use effects obliteration anyway. Note that *SM tape data format is unpublished: even we as *SM administrators don't know how to physically access it. I think your department manager needs to clarify exactly what he wants vs. the standards and protections which prevail for tape data. Richard Sims, BU
