CA Dynam for VSE User Guide

IBM Virtual Tape Facility (VTAPE) Support
IBM limitation when writing to VSAM Virtual Tapes
WRITE can only start at the beginning of a VSAM virtual tape. No rewrite or
overwrite of existing data is possible except from the beginning of a tape.
Once a VTAPE STOP command is issued, the remaining buffer contents is
written to tape, the tape is closed, and an end-of-volume (EOV) indicator is
written. This means no further data can be added to the virtual tape after the
VTAPE STOP is issued.
Therefore, in order to create a multi-file VSAM VTAPE all files must be created
using just one VTAPE START and one VTAPE STOP command. To prevent
Dynam/T from automatically issuing the VTAPE STOP command, specify the
HOLD option for each file of the multi-file set. Use the TDYNASN VTSTOP
command to issue the VTAPE STOP command after all the files of the multi-file
set are created.
The following example assumes your virtual tape CUUs have been defined in
the DTVIRT system option record, and that the necessary VSAM files have
been created. The example creates a 3 file unchained multi-file VTAPE set:
// JOB VTAPE
// EXEC DYNCAT
DEF 'TAPE.VTAPE.1' TAPE NGEN=2 VIRTAPE=VTAPE
DEF 'TAPE.VTAPE.2' TAPE NGEN=2 VIRTAPE=VTAPE
DEF 'TAPE.VTAPE.3' TAPE NGEN=2 VIRTAPE=VTAPE
/*
* CREATE FILE 1
* USE THE HOLD OPTION TO PREVENT AUTOMATIC VTAPE STOP
// TLBL SDDLBL,'TAPE.VTAPE.1,H',,,STACK=A
// UPSI 10000010
// EXEC DYNTEST
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/*
* CREATE FILE 2
* USE THE HOLD OPTION TO PREVENT AUTOMATIC VTAPE STOP
// TLBL SDDLBL,'TAPE.VTAPE.2,H',,,STACK=A
// UPSI 10000010
// EXEC DYNTEST
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/*
* CREATE FILE 3
* USE THE HOLD OPTION TO PREVENT AUTOMATIC VTAPE STOP
// TLBL SDDLBL,'TAPE.VTAPE.3,H',,,STACK=A
// UPSI 10000010
// EXEC DYNTEST
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Chapter 3: Supporting Tape File Management 3–61