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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