Opening an output data set

When you specify unlabeled tape, the system checks the output tape to ensure that the existing first record is not a standard volume label. If the first record is 80 bytes in length and contains the identifier VOL1 in the first 4 bytes, the system checks for the following conditions in the order presented:

RACF authorization
Password protection
Expiration date

If the system-wide RACF tape protection option has been selected, the system checks the alter level authorization to the tape volume. If the tape volume is not defined to RACF, then password protection is checked. If the tape volume is defined and the user is not authorized for ALTER, then the tape is demounted. If the user is authorized for ALTER, then password protection is bypassed.

If the system determines that the volume is password protected, then a message to demount the tape is issued to the operator. Otherwise, the system continues processing by checking the expiration date. If the expiration date is earlier than the current date, then a message is issued to ask to destroy the labels, and the operator can either refuse or allow the use of the tape. If the expiration date is later than the current date, then another message is issued, and again the operator can refuse or allow the use of the tape. If in either situation the operator refuses the use of the tape, then the system requests that another volume be mounted. If the operator accepts the tape, then the system destroys the standard label by writing a tape mark over it, thus providing you with the unlabeled tape you requested.

The installation label anomaly exit, volume label editor exit and DFSMSrmm can prevent standard labelled tapes from being converted into unlabeled tapes.

If the tape volume has been found to be RACF defined and the user has ALTER authorization, then the definition is deleted when the label is destroyed. If the system programmer does not want the system to perform this checking, then the system programmer can replace the label anomaly exit or volume label editor exit.

For more information on the label anomaly exit, label editor routines and the various error conditions that can occur during verification of the first record, see IBM standard volume label editor routines, ISO/ANSI volume label verification and editor routines, and Nonstandard volume label verification and editor routines.

Attention: Performing multiple open and close routines without writing any user data past the end-of-tape marker can result in tape marks being written past the marker. Access methods detect the marker when writing; however, since the creation of empty data sets does not involve access methods, the end-of-tape marker is not detected. This can cause the reel or cartridge to run out of tape.