GTDEXTV

Users migrating volumes to devices with a greater number of primary cylinders can use the automatic ICKDSF EXTVTOC facility of TDMF to invoke the REFORMAT function without the necessity of varying these volumes offline to sharing systems. The GTDEXTV program can be run before the start of a migration to report on the likely effect of this TDMF and ICKDSF processing.

In particular, the program will report:
  • Volume status that would prevent a VTOC reformat attempt by TDMF.
  • The optimum extended VTOC size, as calculated by TDMF.
  • The data sets that must be moved to facilitate the optimal VTOC extension.

GTDEXTV should be run on the same z/OS system as intended for the TDMF Master job, because it might make a prediction based on the level of ICKDSF installed which would not be valid if the TDMF Master was run on another of the participating systems.

The following JCL is required to run the GTDEXTV program:

Figure 1. GTDEXTV JCL
//step      EXEC PGM=GTDEXTV
//STEPLIB   DD DISP=SHR,DSN=<authorized library>
//SYSPRINT  DD SYSOUT=<sysout class>
//SYSIN     DD *
< control statements >
/*

The control statements processed by GTDEXTV have the same format as a TDMF Swap migration. Migration statements contain the following:

  • The word MIGRATE
  • A source volume serial number
  • A target volume serial number

These three items must appear on the same input record.

The program uses the EXCP macro to read the VTOCs of each source and target volume. The source volume's mount status and VTOC indicators are checked for compatibility with the ICKDSF REFORMAT function.

Where a target device has more primary cylinders than are described by the source volume's VTOC, the optimum size to which the VTOC should be extended is:

  • extracted from the EXTVTOC (tracks) option if present in the input stream, or
  • set to be the same as the size of the target volumes, or
  • calculated using the algorithm described in Coexistence with EMC’s z/OS migrator.

If the tracks into which the VTOC would need to extend to achieve this optimum size are currently occupied by data sets, the names of these data sets are reported.