Pathway/iTS TCP and Terminal Programming Guide

Designing Your Application
Compaq NonStop™ Pathway/iTS TCP and Terminal Programming Guide—426751-001
2-22
Dividing Function Between Requester and Server
For further information about designing and coding GDSX processes, refer to the
Extended General Device Support (GDSX) Manual.
Dividing Function Between Requester and Server
In designing a Pathway application, you must decide how to divide function between
requester and server. In making this decision, you should consider the type of requester
or client you are writing (SCREEN COBOL, Pathsend, RSC/MP, or GDSX), and you
should also consider performance, maintainability, and other factors.
For example, what module should check entry fields for validity? If you are writing a
SCREEN COBOL requester, you can easily code it so that the TCP performs these
checks. However, a special edit-checking server could provide better performance.
If your application includes a workstation requester that communicates with servers
using RSC/MP, having the requester check the entry fields would save communications
overhead.
As another example, what module should change screen field attributes such as color,
blink, brightness, or reverse video for such purposes as highlighting an entry field that
contains an error? The SCREEN COBOL language allows such work to be done by the
requester, but it could also be done by the server.
For more considerations about dividing function among modules within an application,
refer to the NonStop™ TS/MP Pathsend and Server Programming Manual.
Designing Server Programs
Request validations, security checks, calculations, database inquiries, and database
changes made in response to a request message are performed by individual units of
code within Pathway server programs. As an application programmer, your task is to
create a server program to perform specific tasks (for example, create a customer
account).
You can write Pathway server programs in C, C++, COBOL85, pTAL, TAL,
FORTRAN, or Pascal in the Guardian environment. Alternatively, you can write
Pathway server programs in C or COBOL85 in the NonStop™ Kernel Open System
Services (OSS) environment; you must program such servers to read the Guardian
$RECEIVE file as described in the Open System Services Programmer’s Guide. In both
cases, you configure and manage the servers by using the PATHCOM interactive
interface or the Pathway management programming interface (based on the Subsystem
Programmatic Interface, or SPI) in the Guardian environment.
Regardless of which operating environment or programming language you use, your
Pathway server programs can access database files through the NonStop™ SQL/MP
relational database management system or the Enscribe database record manager. See
Designing the Database
on page 2-8 for information about these two database managers.
You can use the same server programs, whether developed in the Guardian environment
or in the OSS environment, with several different requester and client interfaces. These
interfaces include SCREEN COBOL, the Pathsend procedures, and the RSC/MP
interface. Requesters or clients using different interfaces can share the same Pathway