Pathway/iTS TCP and Terminal Programming Guide

Introduction to TCP and Terminal Application
Programming
Compaq NonStop™ Pathway/iTS TCP and Terminal Programming Guide—426751-001
1-8
Requesters
•
In distributed environments, server processes provide high performance by allowing
you to use remote servers instead of performing multiple remote I/O operations,
placing transaction processing close to system resources.
Server Classes
Server classes provide the following benefits:
•
You can minimize use of system resources—for example, processes and file
opens—because server classes are shared and highly utilized.
•
You can maximize performance because server classes allow multiple copies of
server processe to run concurrently in multiple CPUs.
•
Based on configuration settings determined by the system manager or operator, the
PATHMON process can dynamically create additional server processes within the
server class to maintain acceptable throughput as the workload increases.
•
By temporarily freezing and stopping the server class and changing configuration
parameters, the system manager or operator can adjust the number of servers that are
active at any one time to suit response-time requirements.
•
The system manager or operator can balance the workload over multiple processes
and across multiple CPUs, which provides fault tolerance in addition to load
balancing—if a CPU fails, the server class is still available.
Requesters
The Pathway application programming environment provides two programming
interfaces for requesters:
•
The Pathsend application program interface (API), provided in the
NonStop™ TS/MP product
•
The SCREEN COBOL language, provided in the Pathway/iTS product
Requesters written using these two interfaces are briefly described in the following
paragraphs. In addition, other Compaq products are available to assist you in writing
requesters and clients that communicate with Pathway servers. These products include
the RSC/MP product for workstation clients and the Extended General Device Support
(GDSX) product for front-end and back-end processes.
Section 2, Designing Your Application
, provides additional information about how
Pathsend requesters, SCREEN COBOL requesters, RSC/MP clients, and GDSX
processes can be used in Pathway applications.
Pathsend Requesters
The Pathsend procedure calls and the LINKMON process allow Guardian processes to
access Pathway server classes. The Pathsend procedures bring the benefits of Pathway
server classes to a wide range of requesters, providing flexibility in application design.
They also provide high performance for requesters that do not need a complex,