VTAM® provides the following
levels of MPC capability:
- High-performance data transfer (HPDT)
HPDT MPC connections
provide more efficient transfer of data than
non-HPDT MPC connections.
They do this by using HPDT services to provide the following functions:
- Data packing without data movement: This process decreases consumption
of CPU cycles by reducing the internal movement of data, thus increasing
the availability of MIPS (million instructions per second) for user
processing.
- Chain scheduling of channel programs: This process reduces operating
system I/O invocations and CPU overhead.
HPDT MPC can also run in HPDT Packing mode. HPDT Packing
reduces data stream fragmentation. See HPDT Packing for more information.
HPDT services are available
over connections to other nodes that implement HPDT MPC. Applications
that use high-performance data transfer services rely on HPDT MPC connections
for path length reductions and performance enhancements when sending
and receiving data. For more information about high-performance data
transfer services, see the z/OS Communications Server: SNA Programmer's
LU 6.2 Guide.
HPDT MPC uses
the services of the communications storage manager (CSM). CSM is a
storage facility that allows authorized host applications to set up
data in buffers that can be addressed and accessed by other authorized
host applications, eliminating the need to copy data as it is being
prepared to be sent. CSM is installed with VTAM. Maximum CSM storage limits are defined
in the CSM parmlib member, IVTPRM00. For more information about CSM,
see Communications storage manager (CSM).
- Non-HPDT
Non-HPDT MPC connections
do not use HPDT services. Non-HPDT MPC connections
can be considered synonymous with APPN host-to-host channel (AHHC)
connections. See Using MPC connections in an APPN network.
- Subarea
Subarea MPC connections are described in Multipath channel connections.
z/OS Communications Server: SNA Network Implementation Guide
Copyright IBM Corporation 1990, 2014