TS/MP Pathsend and Server Programming Manual (H06.05+, J06.03+)

USCODE consists of user exits that are called by TSCODE to handle the application specific, data
communications-related functions, such as data manipulation, protocol conversion, and message
routing for the I/O process. USCODE is typically written in TAL or pTAL and bound with TSCODE
to produce a functional GDSX process.
GDSX provides its own interface to Guardian procedures, TMF procedures, and Pathsend
procedures. The names of the GDSX procedures typically look like their Guardian, TMF, or Pathsend
equivalents, but they have a circumflex (^) character inserted before the procedure name. For
example, SERVERCLASS_SEND_ becomes ^SERVERCLASS_SEND_. The GDSX interface supports
both context-free and context-sensitive Pathsend procedures.
When a GDSX process is used as a front-end process, multiple threads of a usercoded device
handler provide separate tasks to manage the input from I/O devices and provide functions such
as data-stream conversion, implementation of a communications protocol, and network
communications error handling. One instance of the device handler manages one I/O device.
If the GDSX process is acting as a front-end process for a TCP, the GDSX process simulates a
terminal supported by the TCP; the simulated terminal is typically run by an IDS requester program.
When the IDS facility is used, the GDSX process does not ordinarily control how data appears to
the intelligent devices, nor does it perform any other device-dependent functions. However, the
GDSX process can be designed to perform device-dependent functions if needed.
A GDSX process can also act as a front-end process to a LINKMON process or ACS subsystem
processes, as shown in Figure 7 (page 42). The figure shows the path of a transaction from a
general device to a Pathway server through a GDSX process.
In this example, the GDSX device handler contains the application requester logic and uses the
Pathsend interface to communicate with Pathway servers. Normal interaction with a server process
for each thread is similar to that of a Pathsend requester process.
NOTE: Figure 7 (page 42) does not reflect the actual flow of data from the GDSX processes to
the Pathway server class. Only server-class control information is passed to the LINKMON process
or the ACS subsystem processes; the application data moves directly from the GDSX process to
the server class.
Designing Requester Programs 41