Enhancement to USAT processing

TPFUG_Req_Number: S97001
Contact Originator Id: Alan Pope
Abstract: Enhancements for increased functionality within current USAT package.
Description: There are five enhancements to the USAT package that we are recommending:

1) CT26 is hard coded to allocate storage with a protect key of 'F'. The user should be allowed to override this with a new USATC keyword. Default='F'.

2) There is a user option byte IUSAUOP generated by USATC, but there is no keyword in USATC to allow user to code in values.

3) There should be a mechanism to allow the user to allocate read/write protected 'fences' between carved out USAT areas.

4) A method to dynamically add, delete, and update USATC items without the need to load a new Control Program. Typically the SIZE parameter.

5) Sub System support. The carved areas being Sub-System unique.
Solution Considerations: Recommendations 1 and 2 should be straight forward. Item three could be accomplished if item 1 is accepted by coding 'USATC ... PKEY=x8', but we'd then need another option in USATC to prevent fences being added to dump label table. Perhaps a 'USATC FENCE' entry is viable, or to just force CT26 always to build a fence after/before new area.

The location of the USAT table in the CP is inconvenient in an operational system where configurations need to be changed.

The USAT table needs to be available during CTIN processing.

There is also a requirement for Sub System shared and unique capability. Putting USAT table(s) in control program keypoints would seem consistant with other configuration dependent data.

Keypoints are available to CTIN at restart time and also make changing data and loading easy. Keypoints also support Sub System shared/unique data and, importantly, processor unique configuration data.

CINFC is Sub System dependent so no changes are required here.

Checks should be performed at assembly time that the CINFC Sub System attribute is consistant with its use by the USATC macro.

Note that it would seem quite reasonable to allow a Sub System unique CINFC in the shared (BSS) USAT table. This would imply BSS only. This is different to USAT items which allocate main storage in each Sub System (including the BSS).

The CINFC label CMUSER is, currently, reserved for the address of the USAT table. It is also Sub System unique which implies BSS only (given that the IBM design allows for only one table).

If this is to be retained, another CINFC item is required for Sub System unique USAT tables. CMUSER would give the address of the Sub System shared table but would only be accessible to the BSS. This is not unreasonable and would be consistent with the current BSS only design?

A functional entry to display/change/add would be desireable. (also implemented at British Airways).

The CP changes to support Sub Systems is small. CT26 changes were minor, the changes to CT25 about 45 lines of assembler code.