If you want to use the complete space available on the tape and no loinger need any data that may be on the tape, use Overwrite. Remember that OPP is calculated from the time that the last backup set on the tape volume is closed.
If the tape has only been partially used, and you want to keep what is on the tape, but use additional space on the volume, use append. Remember that APP is figured from the time that the first backup set on ther volume is opened.
