Tapes physically wear out after extended use. You can determine if a tape is wearing out by periodically printing the error log. Use the Print Error Log (PRTERRLOG) command and specify TYPE(*VOLSTAT). The printed output provides statistics about each tape volume. If you use unique names (volume identifiers) for your tapes, you can determine which tapes have excessive read or write errors. You should remove these bad tapes from your media library.
If you suspect that you have a bad tape, use the Display Tape (DSPTAP) or the Duplicate Tape (DUPTAP) command to check the integrity of the tape. These commands read the entire tape and detect objects on the tape that the server cannot read.