Hello,
Backup exec takes tapes depending on the OPP and AP set on the tape, in conjunction with the job settings, if the job is to append it looks for an appendable tape else overwritable tapes.
If there are more than one tapes matching these requirements, it will pick up the tape depending on the allocation date.This depends on when the tape was added to the media set.You may create a media rotation policy accordingly.refer to the admin manual for more details.
http://support.veritas.com/docs/237374
http://support.veritas.com/docs/192265
http://support.veritas.com/docs/263945
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