Verify your media

Good save procedures ensure that you verify that you use the correct media. Depending on the size of your installation, you may choose to manually verify media, or you may have the server verify the media.

Manual checking: You can use the default of *MOUNTED for the volume (VOL) parameter on the save commands. This tells the server to use the currently mounted media. It is up to the operator to load the correct media in the correct order.
System checking: You specify a list of volume identifiers on the save or restore commands. The server makes sure that the operator loads the correct media volumes in the order specified on the command. If an error occurs, the server sends a message to the operator that requests the correct media volume. The operator can either load another media or override the request.

Expiration dates on the media files are another method that you can use to verify that you use the correct media. If you rely on your operators to verify the media, you might specify an expiration date (EXPDATE) of *PERM (permanent) for your save operations. This prevents someone from writing over a file on the media unintentionally. When you are ready to use the same media again, specify CLEAR(*ALL) or CLEAR(*REPLACE) for the save operation. CLEAR(*REPLACE) automatically replaces active data on the media.

If you want the server to verify your media, specify an expiration date (EXPDATE) that ensures that you do not use the media again too soon. For example, if you rotate five sets of media for daily saves, specify an expiration date of the current day plus 4 on the save operation. Specify CLEAR(*NONE) on save operations so the server does not write over unexpired files.

Avoid situations where the operator must regularly respond to (and ignore) messages such as "Unexpired files on the media". If operators get in the habit of ignoring routine messages, they might miss important messages.