Data Set Processing

When access to an existing data set is attempted, Control-M/Tape checks the entire data set name supplied in the JCL against the entries in the Media Database. The operating system compares only the last 17 characters against the data set header label.

When an output request is issued for multi-data set volumes, Control-M/Tape checks that the file sequence is valid:

• A file can be created only if the previous file sequence number exists.
• A file cannot be overwritten if files with higher sequence numbers exist.

If, during a read or update request for an existing data set, the data set is not found in the Media Database, Control-M/Tape can optionally define the data set dynamically. This can happen if the data set was created outside Control-M/Tape control (for example, at another site).