5.1: Virtual storage constraint relief

Virtual storage constraint relief (VSCR) is the reduction of virtual storage usage, which helps avoid short-on-storage conditions and can reduce the need for more CICS regions. CICS® TS 5.1 provides VSCR in a number of areas, which reduces pressure on 24-bit and 31-bit virtual storage.

This section describes virtual storage improvements for the following areas:

  • 24-bit virtual (below the line)
  • 31-bit virtual (above the line but below the bar)
  • 64-bit virtual (above the bar)

24-bit storage

The following CICS infrastructure items now use 31-bit storage in place of all, or some, of the 24-bit storage that was used in previous releases:

  • Sync point and back out processing.
  • Processing for transient data EXEC CICS application programming commands, wherever possible.
  • CICS execution diagnostic facility (CEDF).
  • CICS command-language tables for command interpreter (CECI) and other functions.
  • Processing for journaling EXEC CICS application programming commands.
  • Processing for function-shipped DL/I calls.
  • Mirror transactions. For more information, see Mirror transactions.
  • The COMMAREA on an EXEC CICS XCTL call. For more information, see XCTL with a communication area.

For more information about items that are improved in CICS TS 5.1, see Reduced use of 24-bit storage in CICS TS V5.1.

31-bit storage

The following CICS infrastructure items now use 64-bit storage in place of all, or some, of the 31-bit storage that was used in previous releases:

  • Console queue processing
  • Storage allocation control blocks
  • Loader control blocks

For more information about changes in the use of 31-bit storage, see Changes in CICS storage use from 31-bit to 64-bit storage in CICS TS V5.1.

64-bit storage

In CICS TS 5.1, the new managed platform and application context CICS facilities use 64-bit virtual storage.

User applications can now directly access 64-bit storage. For more information, see 64-bit application support: CICS TS V5.1.

Mirror transactions

The mirror transactions (CEHP, CEHS, CPMI, CSHR, CSMI, CSM1, CSM2, CSM3, CSM5, and CVMI) are now defined as TASKDATALOC(ANY).

XCTL with a communication area

When a communication area (COMMAREA) is used with an EXEC CICS XCTL command, CICS can now create the COMMAREA in 31-bit storage, rather than 24-bit storage, where appropriate.

When EXEC CICS XCTL is used, CICS ensures that any COMMAREA is addressable by the program that receives it by creating the COMMAREA in an area that conforms to the addressing mode of the receiving program. If the receiver is AMODE(24), the COMMAREA is created in 24-bit storage. If the receiver is AMODE(31), the COMMAREA is created in 31-bit storage.

In earlier releases of CICS, the COMMAREA was always copied into 24-bit storage.

User exit global work area

The EXEC CICS ENABLE PROGRAM system programming command has the new attribute GALOCATION that specifies the location of the storage that CICS provides as a global work area for this exit program. The GALOCATION attribute can have one of the following values:
LOC24
The global work area is in 24-bit storage. This location is the default location.
LOC31
The global work area is in 31-bit storage.

For more information about the EXEC CICS ENABLE PROGRAM system programming command, see ENABLE PROGRAM command.