TS/MP Pathsend and Server Programming Manual (G06.24+, H06.03+)

Designing Your Application

NonStop TS/MP Pathsend and Server Programming Manual–132500

2-19

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, or GDSX), and you should

also consider performance, maintainability, and other factors.

For example, which program 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, having the requester check the entry fields would save communications

overhead.

As another example, which program 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,

see Packaging Server Functions

, under Designing Server Programs, later in this section.

Designing Server Programs

Request validations, security checks, calculations, database inquiries, and database

changes made in response to a request message should be 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, Pascal, TAL, pTAL,

FORTRAN, or Extended BASIC 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 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. Refer

to Designing the Database

earlier in this section 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, the Remote Server Call

(RSC) interface, and the Pathway Open Environment Toolkit (POET). Requesters or

clients using different interfaces can share the same Pathway server classes if you ensure

that the server program’s request and reply formats are consistent for all requesters.