Establishing cross memory communication

Before cross memory communication can take place, the service provider must establish the cross memory environment. The service provider does this by supplying PC routines and by issuing the MVS macros that establish the necessary linkages and authorizations.

The macros the service provider issues to establish, disconnect, or destroy the cross memory environment are:
  • ATSET
  • AXEXT
  • AXFRE
  • AXRES
  • AXSET
  • ETCON
  • ETCRE
  • ETDEF
  • ETDES
  • ETDIS
  • LXFRE
  • LXRES
The actual set of macros the service provider must issue depends on the following:
  • Whether the services will be available to all address spaces or to selected address spaces only
  • Whether the PC routine is space switch or non-space switch.

The service provider must issue these macros from a program that is running in supervisor state or with a PSW-key mask of 0-7, and is enabled, unlocked, and in primary ASC mode.

In addition to the previously listed macros, the service provider might also issue the PCLINK macro. The PCLINK macro enables a basic PC routine to save and restore the user's environment. Only basic PC routines that are in supervisor state are permitted to issue the PCLINK macro.

These macros are fully described in one of the following:
Note: Installations that currently build their own PC routine definitions and use IHAETD to map the format 0 ETD may continue to do so. IBM® recommends the use of the ETDEF macro, however.