Input Trailer Label Routines (NSLETRLI)

When a tapemark is encountered on an input tape, data management's EOV routine gives control to your routine for processing input trailer labels, except when:

The force end-of-volume (FEOV) macro instruction is used to force an end-of-volume condition.
At the end of the data set, the DCB exit list indicates deferred nonstandard input trailer label processing.

When your routine receives control, the tape is already positioned for label processing:

For forward read operations, the tape is positioned immediately after the tapemark at the end of the data set.
For backward read operations, the tape is positioned immediately before the tapemark at the beginning of the data set.

Your routine does not need to reposition the tape before returning control to the control program.

If additional volumes are specified in the JFCB the control program uses the next-specified volume serial number and performs volume switching. (You specify the volume serial numbers in forward sequence, regardless of whether the tapes are to be read forward or backward.) If the new volume is not already mounted, the control program issues a mount message to the operator. The new volume is then processed by the EOV routine and your input header label processing routine.

If another volume is not specified in the JFCB, the control program gives control to the user's end-of-data-set (EODAD) routine that is specified in the DCB. Subsequently, the processing program or the operating system closes the data set. When an input data set is closed, your output trailer label routine is given control. This allows you to position the tape if necessary. When an end-of-data-set condition occurs and the DCB exit list (EXLST) indicates deferred nonstandard input trailer label processing, the close routine passes control to your input trailer label routine before passing control to your output trailer label routine. The DCB exit list is described in z/OS V2R1.0 DFSMS Using Data Sets.

The modeset byte is moved from a 24–bit UCB address to a 31–bit UCB address if you request the XTIOT UCB NOCAPTURE option and the NON-VSAM_XTIOT option is set to yes. OPEN, EOV, and CLOSE will always turn DEB31UCB on in the work area to signify that DXDEBUCB is a 31–bit UCB address. Although the UCB address field will be four bytes, it typically will contain a three-byte address.