NET/MASTER Network Control Language (NCL) Programmer's Guide

Pathway, NonStop NET/MASTER MS, and NCL
Working With Pathway Server Classes
15–4 106160 Tandem Computers Incorporated
PATHMON and PATHCOM Figure 15-1 shows the Pathway Monitor (PATHMON) and PATHCOM processes.
PATHMON is the central control process for a Pathway system. It is the first Pathway
process started. PATHCOM is the command language interface used to communicate
interactively with PATHMON to configure and control a Pathway system. After
starting PATHMON, you can start PATHCOM and open communication with
PATHMON.
Refer to the Pathway PATHCOM Reference Manual for more information on starting
PATHMON and PATHCOM processes.
Requesters and Servers Transaction processing applications in a Pathway system consist of two types of
programs: requester programs and server programs. Requesters and servers
communicate using the Tandem NonStop Kernel message system. Figure 15-1 shows
both requester processes and server processes.
Requester programs are usually written as SCREEN COBOL programs, which are
coordinated by a terminal control process (TCP). A Pathway requester process is a
process that makes requests of a server process. Examples of requests are adding,
updating, inserting, and deleting data in a database.
Requests originate from users and processes. A user can enter requests from a
Pathway terminal or PC. The requests are then routed to the Pathway requester by
SCREEN COBOL directives or by Pathway’s intelligent device support (IDS) interface.
The Pathway requester program then issues a SEND statement to send standard
operating system messages to the appropriate server class. A request is sent to a
server process as a request message.
Server programs are developed by application programmers using COBOL85, TAL,
MUMPS, FORTRAN, BASIC, C, or Pascal. A Pathway server process is a process that
typically controls access to a database, implements database requests, and returns
replies to the requester. An example of a reply is that a record was successfully added
to a database. A server class is a collection of replicated server processes, in which all
server processes in a server class provide the same set of functions.
Refer to the Pathway SCREEN COBOL Reference Manual and the Pathway SCREEN
COBOL Utility Program (SCUP) Reference Manual for more information about SCREEN
COBOL. Refer to the Introduction to Pathway and introductory sections in other
Pathway manuals for general information about requesters and servers.
The PATHSEND Interface There are many situations where it is advantageous to have a device (terminal or PC)
talking directly to the Pathway server class without an intervening Pathway TCP or
requester. This may be for increased performance or because the requesting process is
not written in SCREEN COBOL.
Requester programs can be written in languages other than SCREEN COBOL, such as
TAL, C, COBOL85, Pascal, or NCL. When a requester program is written in one of
these languages, the PATHSEND interface, shown in Figure 15-1, provides access to
Pathway server classes. A requester written using the PATHSEND interface is called a
PATHSEND requester.