Using BSAM, BPAM, and QSAM support for XTIOT, uncaptured UCBs, and DSAB above the 16 MB line

In z/OS V1R12, BSAM, BPAM, QSAM and OCE were enhanced to support the existing XTIOT (extended task input/output table), UCB nocapture, and DSAB-above-the-line options of dynamic allocation. Previously, VSAM and EXCP were the only access methods to support these dynamic allocation options. In V1R12 the EXCP support was enhanced and BSAM, BPAM and QSAM support was provided. This support applies to dynamic allocation of DASD, tape, and dummy data sets, and cases where PATH= is coded. EXCP support including the EXCPVR and XDAP macros is also affected. These enhancements provide virtual storage constraint relief especially in the areas of DASD and tape support, and enable you to have more than about 3200 dynamically-allocated data sets.

To exploit these enhancements, the following types of programs must be changed and installations using them must set to YES the DEVSUPxx PARMLIB option NON_VSAM_XTIOT:
  1. Those programs that call dynamic allocation and want to exploit XTIOT (extended task input/output table), UCB nocapture, and DSAB-above-the-line options of dynamic allocation. They must check that DFAXTBAM is set on before they exploit any of these dynamic allocation options. This bit signifies that the installation enables this function by setting the option in the DEVSUPxx member of PARMLIB.
  2. Those programs that issue OPEN or RDJFCB for data sets which might have been dynamically allocated with XTIOT (extended task input/output table), UCB nocapture, or DSAB-above-the-line options of dynamic allocation. These programs need to either:
    • Have no dependency on the dynamic allocation options at all, and so need to specify a new DCBE macro LOC=ANY option, or
    • Have dependencies on dynamic allocation in order to support XTIOT, uncaptured UCBs, and DSAB above the line. These changes MUST be made prior to using the new DCBE macro LOC=ANY option.

If the system programmer does not set NON_VSAM_XTIOT=YES, then application programs cannot use the three options of dynamic allocation for data sets with BSAM, QSAM, or BPAM DCBs. In this case, those programs will continue to fail with existing error message IEC133I when opening the files dynamically allocated with the XTIOT (extended task input/output table), UCB nocapture, or DSAB-above-the-line options of dynamic allocation. Application programs that use the three options of dynamic allocation for data sets with EXCP DCBs will experience no difference.

The following sections list the tasks and associated procedures for using these enhancements.