IBM AS/400 - Manual (Page 23)

Chapter 4. Communications applications
Communications applications that are used in an APPC (advanced program-to-program) environment are
also available to be used in an APPN and HPR environment; only the method by which data is transported
is changed. APPC delivers the data from applications higher in the SNA layers down to APPN for
transportation through the network. User-written APPC applications and distributed data management
(DDM) are fully supported in an APPN and HPR environment. The topic, Application programming
interface (API) performance considerations gives a more complete discussion of APPC applications.
When you encounter problems that indicate that the route to the remote location cannot be found, you can
attempt to make the connection again with the Start Pass-Through (STRPASTHR) command. See the
topic, Solving remote communication problems using STRPASTHR for more information.
For information on Connecting Windows 95/NT Clients to your AS/400, see Client Access.
User written APPC applications
APPN performs many functions in a communications environment. Therefore, it is important to consider
time-out parameters in APPC programs which use ICF. In particular, it may be important to increase the
WAITFILE parameter for these applications so that they do not time-out while waiting for APPN functions
to be performed.
APPN function is transparent to APPC programs using APPN take advantage of the following routing
functions:
v Non-adjacent nodes appear adjacent and so APPC programs may communicate directly to programs in
non-adjacent nodes (without any APPC programs on the intermediate nodes).
v Performance is improved for APPC programs with session endpoints that are not physically adjacent in
the network.
v APPC programs may communicate directly to programs in nodes in an adjacent APPN network through
network nodes.
Distributed data management (DDM)
DDM is a function of the operating system that allows an application program or user on one system to
use database files stored on remote systems. The systems must be connected by a communications
network, and the remote systems must also be using DDM.
DDM on the AS/400 allows application programs or users to:
v Access data files that reside on remote systems (target systems). The remote systems can also access
data files on the local AS/400 system.
v An application can add, change, and delete data records in a file that exist on a target system.
v Create, delete, or rename files on a remote system.
v Copy a file from one system to another.
When DDM is in use, neither the application program nor the program user needs to know if the file that is
needed exists locally or on a remote system. Remote and local file processing are essentially handled the
same way.
Application program interface (API) performance considerations
To achieve better performance with your AS/400, you need to consider the application programming
interface (API) available on the AS/400. To optimize APPC performance, consider the following:
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