Compatibility with FSU II

IMS High Performance Unload supports compatibility with IMS/VS Fast Scan Utility II Version 2 (FDP 5798-DFN, also referred to as FSU II).

FABHFSU provides the following compatibility with FSU II:

  • FABHFSU output data sets are compatible with FSU II output data sets.
  • Under FABHFSU, FSU II user exit routines can run without changes and without recompilation. The user exit routine must not access or modify internal, undocumented FSU II control block information.
  • FABHFSU can often use the same PSBs as FSU II (see PSBGEN compatibility for details some minor modifications might be required).
  • FSU II control statements can usually be used without changes for FABHFSU. They might require minor changes if the different PCBs used to control the content of the output data sets are not contained in the same PSB.
  • IMS High Performance Unload provides the aliases shown in the following table for the FSU II modules. These aliases allow the FSU II JCL to run the FABHFSU PSF.
Table 1. Aliases for FSU II modules
Name in IMS High Performance Unload Name in FSU II
FABHPSFM FSUMAP
FABHPSFC FSUCTRL
FABHPSFS FSUSUMM

PSBGEN compatibility

To ease conversions from FSU II to FABHFSU, some PSBGEN restrictions do not apply to FABHFSU.

For example:

  • The PROCOPT statement fields on the PCB and SENSEG statements can have any value acceptable to IMS.
  • Field sensitivity can be specified during PSBGEN, but is ignored by FABHFSU.

CON control statement

The CON control statement in CARDIN data set for FABHFSU, which activates the concatenate option, allows you to run some FSU II user exit routines under FABHFSU. The exit routines expect to find the segment prefix and the segment data concatenated in contiguous virtual storage.

0........1.........2.........3.........4.........5.........6.........7.........8
12345678901234567890123456789012345678901234567890123456789012345678901234567890

CON
Position
Description
1
Code the CON keyword to activate the concatenate option.

When you invoke a user exit routine, both FABHFSU and FSU II pass the address of the segment prefix and the segment data to the user exit routine. For FSU II, the segment prefix and the segment data are contiguous in virtual storage. With FABHFSU, the segment prefix and the segment data are not contiguous in virtual storage.

The CON control statement instructs FABHFSU to concatenate the segment prefix and the segment data in contiguous virtual storage, before invoking the user exit routine.

Since concatenation requires additional CPU cycles, use the CON control statement only for user exit routines that access both the segment prefix and the segment data and assume both are contiguous in virtual storage.