GDSX Manual

Design and Development
Extended General Device Support (GDSX) Manual–134303
2-9
User Tasks
ProcDel Task
The Process Deletion task is created temporarily to oversee the stopping, cleanup, and
deletion of another task that is to be stopped or abnormally ended (abended).
User Tasks
Following are descriptions of the different types of user tasks:
DEVICE^HANDLER Task
A DEVICE^HANDLER is a required, user-customized procedure typically used to
modify the communication of each thread between a requester and another file (often a
terminal). Running copies of DEVICE^HANDLER code are called
DEVICE^HANDLER tasks. These tasks are separate entities although they all use the
same DEVICE^HANDLER procedure code. DEVICE^HANDLER tasks are also called
term tasks.
In a GDSX application there is usually one DEVICE^HANDLER task created for each
terminal or device configured. A DEVICE^HANDLER task is created when a requester
process opens a dynamic SU through GDSX or when a preconfigured device or
subdevice is started.
LINE^HANDLER Task
A LINE^HANDLER is an optional USCODE procedure typically used to implement
data communications protocols and to allow each requester thread to use a shared
resource (often a communications line) without allowing the threads to interfere with
each other. Running copies of LINE^HANDLER code are called LINE^HANDLER
tasks. These tasks are separate entities although they all use the same
LINE^HANDLER procedure code. LINE^HANDLER tasks are also called LINE tasks.
Using a LINE^HANDLER to provide line protocol functions is necessary only if the
access method to which GDSX interfaces does not provide these functions. For
example, LINE^HANDLER functions are required within GDSX where GDSX
interfaces to multidrop Envoy; however, they are not required where GDSX interfaces to
AM3270.
In a GDSX application there is usually one LINE^HANDLER task created for each line
configured. A LINE^HANDLER task is created when a user starts a preconfigured line
by means of SCF. The maximum number of LINE^HANDLER tasks, specified by the
MAXLINES configuration parameter, is 15.
Although a LINE^HANDLER is often used to handle messages to or from a
communication line, a LINE^HANDLER procedure may also be used to route messages
to an external process.
Overview of GDSX Processing
TSCODE does the following at GDSX process initialization time:
1. Initializes configuration parameters from default values.