When a process opens a tape file, the process can become suspended even if the requested tape is already mounted on an available tape drive. The suspension occurs if the process does not give the system sufficient information to identify the particular tape to search for the file. If the process becomes suspended, the operator can use system commands such as IL (Ignore Label) or OU (Output Unit) to specify the correct tape drive so process execution can resume.

Nothing you can do removes the need for someone to mount a tape containing the tape file on a tape drive. However, you can ensure that an operator does not have to take any further action beyond mounting the tape and later removing it.

You can use the SERIALNO attribute to specify the particular tape that should be opened. When the process attempts to open the file, the system checks to see whether a tape with that SERIALNO value is mounted on any of the available drives. If the tape is mounted, then the system looks for the requested file on that tape, without ever suspending the process.

SERIALNO is also available as an option in the WFL COPY statement. The following is an example:

COPY (JASMITH)= FROM SYSPK(PACK) TO LABCON(TAPE,SERIALNO=“LABIN”);

This example creates a tape named LABCON with a SERIALNO value of LABIN. The SERIALNO value can include letters as well as digits. Any letters in the string must be capitalized.

Sometimes you want the program to write output to a tape, but you do not really care which tape, as long as it goes to a tape that is not otherwise in use. In this case, you can leave the SERIALNO value empty and set the MYUSE file attribute to OUT. If the SERIALNUMBER operating system option is not set, then the system writes the file to any scratch tape that is mounted and not in use. If you specify the SCRATCHPOOL or DENSITY file attributes, the system restricts the selection to tapes with the requested scratch pool or density.

An operator can set or reset the SERIALNUMBER option with the OP (Options) system command.