TS/MP 2.5 Pathsend and Server Programming Manual

SCREEN COBOL requestors that employ the IDS facility within the TCP send data back and forth
between the Working-Storage Section and an intelligent device (or a front-end process that controls
the device) by way of message templates defined in the Message Section. IDS requestors use
SCREEN COBOL SEND MESSAGE statements and their associated REPLY clauses in the Procedure
Division to interact with the intelligent devices or front-end processes.
Although IDS sends and receives data through Message Section templates instead of Screen Section
templates, the TCP still provides:
• Link management for access to Pathway server-classes
• TMF support to ensure transaction protection and database integrity
• Fault tolerance through process pairs
• Multithreading and multitasking
• Expanded I/O editing support for data streams from intelligent devices
For information about designing and coding IDS requestors, see the Pathway/iTS TCP and Terminal
Programming Guide.
Pathsend Requestors
As an alternative to writing SCREEN COBOL requestors, you can write Pathsend requestors in C,
C++, COBOL85, Pascal, TAL, or pTAL. In such requestors, you use Pathsend procedure calls to
communicate with Pathway servers. The ACS subsystem processes manage links to your server
processes on behalf of Pathsend requestors.
Design Considerations
Pathsend requestors are a good choice for your applications if you need to:
• Take a high volume of transactions from a limited number of devices. In this scenario, there
are relatively few requestor processes, the requestors are busy, and configuration and
management is minimal.
• Access servers that are shared by Pathway requestors and applications other than OLTP
applications: for example, a security checking server or a logging server. If such servers are
used infrequently or if the workload varies, server processes can be automatically deleted
when not needed and restarted through the PATHMON process when needed again.
• Access servers from environments containing a mix of online transaction processing and batch
processing; that is, environments where the same set of servers handle both online requests
and requests from batch applications such as NetBatch Plus processes.
• Write nested servers, which act as requestors by making requests to servers in other
server-classes, perhaps server-classes managed by a different PATHMON process.
• Write context-sensitive servers, which are discussed later in this chapter under “Designing
Server Programs.”
Pathsend procedure calls give you more flexibility than WRITEREAD calls for serverto- server
communication. The application gets all the advantages of server-classes, including advantages
not readily available with WRITEREAD; for example, load balancing, adjusting the number of
servers to fit response-time requirements, and configuration and operations management. You can
use the Pathsend procedure calls in C, C++, COBOL85, Pascal, TAL, and pTAL programs.
The Pathsend procedures and the ACS subsystem processes, however, do not provide multithreading,
fault tolerance, device configuration, or operations management for requestors. Therefore, if you
need these capabilities in a Pathsend requestor, you must provide the programming for them.
In addition, Pathsend procedure calls that send messages to server-classes must be protected by
the TMF subsystem to ensure data integrity in your Pathway application.
36 Designing Your Application