TS/MP 2.5 Pathsend and Server Programming Manual

• 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 a time to
suit response-time requirements.
• The system manager or operator can balance the workload over multiple processes and across
multiple processors, which provides fault tolerance in addition to load balancing: if a processor
fails, the server-class is still available.
Requestors
The Pathway application programming environment provides two programming interfaces for
requestors:
• The Pathsend API, provided in the TS/MP product
• The SCREEN COBOL language, provided in the Pathway/iTS product
Requestors written using these two interfaces are briefly described in the following paragraphs. In
addition, other HP products are available to assist you in writing requestors and clients that
communicate with Pathway servers. These products include the RSC/MP product and, the POET
for workstation clients, and the Extended General Device Support (GDSX) product for front-end
and back-end processes.
chapter 2, “Designing Your Application” (page 28), provides additional information about how
Pathsend requestors, SCREEN COBOL requestors, RSC/MP and POET clients, and GDSX processes
can be used in Pathway applications.
Pathsend Requestors
The Pathsend procedure calls and the ACS subsystem processes allow Guardian processes to
access Pathway server-classes. The Pathsend procedures bring the benefits of Pathway server-classes
to a wide range of requestors, thereby providing flexibility in application design. They also provide
high performance for requestors that do not need a complex, multithreaded interface for terminals
or intelligent devices. Finally, they provide support for both context-free and context-sensitive servers.
Pathsend requestors support these features:
• Use of the TMF subsystem
• Automatic retry of I/O operations to a server process if the primary process of a server process
pair fails, through use of the Guardian file system
The GDSX product provides a set of “pseudo Pathway procedures” that allow you to call Pathsend
procedures in the user-supplied part of a GDSX program. A GDSX process can therefore function
as a Pathsend requestor. GDSX processes can communicate with devices by means of a number
of data communications protocols, as described in the Extended General Device Support (GDSX)
Manual.
SCREEN COBOL Requestors
SCREEN COBOL requestors, which are compiled by the SCREEN COBOL compiler and then
interpreted and executed by the TCP, provide ease of programming if you need to handle large
number of terminals or intelligent devices, or if you need screen presentation services. The TCP
and the SCREEN COBOL language produce a highquality, manageable application. The TCP
provides multithreading of requestors, fault tolerance, terminal device configuration, and operations
management so that you do not need to program these features in your application. Transaction
protection through use of the TMF subsystem, with simplified programming, and automatic retry
of I/O operations are also provided. SCREEN COBOL requestors are described in the Pathway/iTS
TCP and Terminal Programming Guide and the Pathway/iTS SCREEN COBOL Reference Manual.
Pathway Applications 21