Checking the next volume

When volume switching is performed for multiple volume input, the EOV routine checks the volume and header labels on the new volume, to ensure that the correct volume is mounted.

The method of locating and checking the HDR1 label varies according to the situation. The processing depends on whether the data set is a continuation of a multivolume data set or is a concatenated data set with like characteristics. Data sets with like characteristics can be processed correctly using the same DCB, input/output block (IOB), and channel program.

Multivolume data set: The data set sequence number is irrelevant for the second and subsequent volumes of a multivolume data set. The EOV routine assumes that the data set continues at the beginning of the new volume and, therefore, checks the first header label group on the tape. The HDR1 label is checked in the same manner as when the data set was opened on the first volume. Processing is abnormally terminated if:
- The data set name is not the same
- The volume is password protected, no previous volume in the data set was password protected, and the system operator or TSO user is not able to enter a correct password.
Note: For volumes residing in an IBM automated tape library, or manual tape library, password protection processing of the data tape set is bypassed. These tapes can be protected with RACF.
Concatenated data sets: The EOV routine handles concatenated data sets with like characteristics. Such data sets are not necessarily the first on the volume, so the EOV routine positions the tape according to the specified data set sequence number. This positioning is the same as for opening a data set. The HDR1 label is checked as it was when the first data set was opened.

The HDR2 label on the new volume is not processed. The data set characteristics that were established when the data set was opened apply to all subsequent volumes handled by the EOV routine. However, the HDR2 label is validated for Version 3 standards.

The data set's block count is not accumulated from volume to volume. It is initialized and verified separately for each volume.