SL-NAME Concept

When checking in external volumes, the volser of a volume being checked-in may be identical to the volser of a volume already in the Media Database. This creates a problem because the volser must be a unique identifier of a volume in the Media Database.

To solve this problem, Control-M/Tape uses fields VOLSER and SL-NAME (Standard Label Name) to provide MVS override logic, as described below:

When checking in a volume (normally by screen TC), the user should:

• Assign a new, unique volser to the checked-in volume. This volser is specified in field VOLSER.
• Specify the original volser (the volser in the Standard Label of the volume) in field SL-NAME.
• Specify the new (unique) volser on the label physically applied to the tape (meaning, the gummed label).

From this point on, the new volser is used to identify the volume (including in the MVS Catalog if cataloged, JCL references to the volume, and so on).

When a job requests a specific volume by JCL, the operating system checks that the volser on the volume’s standard label matches the requested volser to ensure that the mounted volume is the volume that was requested.

If the requested volser and the standard label of the mounted do not match, the operating system normally rejects the volume. However, when a volume is defined in Control-M/Tape with different values in the SL-NAME and VOLSER fields, Control-M/Tape intervenes in operating system processing.

In this case, if the value in field SL-NAME matches the volser in the mounted tape’s standard label, Control-M/Tape allows the volume to be accepted by the operating system.

Note:

The SL-NAME mechanism works only for standard label tapes.

An operator must not mount an SL-NAME volume in response to a request for a scratch tape. If an SL-NAME volume were mounted as a scratch tape, Control-M/Tape would incorrectly update the volume record (in the Media Database) whose volser matches the volser in the SL-NAME volume’s standard label.

The SL-NAME mechanism is intended only for reading tapes. Do not write or rewrite to an SL-NAME volume. When you overwrite a volume, MVS rewrites the volume’s label. For an SL-NAME volume, this would replace the volume’s original volser with the volser requested in the JCL.