Loader domain (LD)

The loader domain is used by the domains of the CICS® system to obtain access to storage-resident copies of nucleus and application programs, maps, and tables. In order to provide this, the loader domain interfaces with MVS™ to perform the loading of programs into the CICS dynamic storage areas (DSAs), and the scanning of the MVS link pack area (LPA).

The most common functions provided by the loader domain are:

ACQUIRE_PROGRAM
used to obtain the load point and entry point addresses and length of a usable program copy, and to reserve the copy for use by the caller.
RELEASE_PROGRAM
used to inform the loader domain that a specific program copy is no longer required.
DEFINE_PROGRAM
used to inform the loader domain of the CICS attributes of a program.
REFRESH_PROGRAM
used to request the loader domain to rescan the LPA or DFHRPL library for a new copy of a program.

The loader domain is utilized by many domains in the system, but its most common user is the program manager domain, for access to application programs. The program manager domain issues the following requests:

ACQUIRE_PROGRAM
whenever a program issues a LINK, XCTL, or LOAD command to link to, transfer control to, or load another program.
DEFINE_PROGRAM
as part of a request to define or autoinstall a program, mapset, or partitionset.
RELEASE_PROGRAM
whenever a called program issues a RETURN command to return control to the calling program, or a program issues a RELEASE command to release a loaded program.
REFRESH_PROGRAM
as part of an EXEC CICS SET PROGRAM NEWCOPY or PHASEIN request.
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