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

SCREEN COBOL Requesters
SCREEN COBOL requesters, which are compiled by the SCREEN COBOL compiler and then
interpreted and executed by the TCP, provide ease of programming if you need to handle large
numbers of terminals or intelligent devices or if you need screenpresentation services. The TCP and
the SCREEN COBOL language produce a highquality, manageable application. The TCP provides
multithreading of requesters, fault tolerance, terminal device configuration, and operations
management so that you do not need to program these features in your application. Transaction
protection through use of the TMF subsystem, with simplified programming, and automatic retry
of I/O operations are also provided. SCREEN COBOL requesters are described in the Pathway/iTS
TCP and Terminal Programming Guide and the Pathway/iTS SCREEN COBOL Reference Manual.
You can use a GDSX process as a front-end process to the TCP and SCREEN COBOL requesters
to communicate with devices not directly supported by the TCP. Use of the GDSX product is
described in the Extended General Device Support (GDSX) Manual.
The Pathsend Environment
The Pathsend environment includes Pathsend processes and LINKMON processes or ACS subsystem
processes:
• Pathsend processes, written as part of your application, use Pathsend procedure calls to make
requests to server classes.
• LINKMON processes or ACS subsystem processes, supplied by HP, control communication
between Pathsend processes and Pathway server classes.
Pathsend Processes
In writing programs to run as Pathsend processes, you use a set of procedures that are part of the
Guardian procedure library. These procedures allow you to send request messages to server
processes within a server class and to receive the servers’ replies. You can call the Pathsend
procedures from programs written in C, C++, COBOL85, Pascal, TAL, or pTAL.
Pathsend procedure calls are provided for both context-free and context-sensitive communication
with servers. A context-free server accepts a single message from a requester, performs the requested
tasks, and issues a single reply to respond to the requester. After the reply message is issued, the
server retains no information (context) that can be used in subsequent requests. A context-sensitive
server engages in a multiple-message communication, or dialog, with a requester. Between
messages, the server retains information (context) pertaining to the dialog.
The use of the Pathsend procedure calls is described in Section 3, “Writing Pathsend Requesters”
(page 51), and their syntax is described in Section 5, “Pathsend Procedure Call Reference”
(page 75). Design considerations related to context-free and context-sensitive servers are discussed
in Section 2, “Designing Your Application” (page 29).
LINKMON Processes
LINKMON processes, together with the PATHMON process, perform link-management functions
for Pathsend processes. (A link is a connection to a server process.) A LINKMON process executes
in each processor, or CPU, of a system. As a link manager, a LINKMON process is responsible
for managing links on behalf of all the Pathsend processes executing in its processor.
If you have the TS/MP software installed on your system, a LINKMON process is automatically
started in each processor. You cannot start a LINKMON process with a RUN command.
Figure 2 (page 24) shows a sample Pathsend environment in which Pathsend processes and a
LINKMON process reside in the same processor on system \A. The LINKMON process sets up
communication to the Pathway server class on system \B through the PATHMON process controlling
the server class. The role of the PATHMON process in establishing this communication is described
in Section 3, “Writing Pathsend Requesters” (page 51).
The Pathsend Environment 23