Availability Guide for Application Design

Availability in the Pathway Transaction-Processing
Environment
Availability Guide for Application Design—525637-004
6-24
Availability Through Pathway/iTS
Operational Concerns
Consider the following operational concerns when designing a Pathsend application:
•
If you decide to use neither process persistence nor process pairs in your Pathway
requester design, then operations staff might need to take responsibility for getting
failed Pathway requesters restarted. Restarting the application clearly implies a
lower level of availability if a failure occurs than you would get through process
persistence or process pairs but saves in development costs.
•
If you choose to rely on operator restart to recover from a stopped Pathway
requester, a well-instrumented application can speed up recovery by bringing the
stopped process to the immediate attention of an operator or helping to apply an
automated solution. Instrumentation can also help recover from the case where
both members of a process pair fail. Refer to Section 8, Instrumenting an
Application for Availability, for details.
Availability Through Pathway/iTS
The Pathway/iTS product contains a terminal control process (TCP) and a COBOL
compiler. The TCP is a multithreaded requester process that interprets a COBOL
program in each thread.
This subsection introduces the Pathway/iTS product and its availability features. First,
it provides an overview of how applications that use the Pathway/iTS product normally
function and includes a skeletal work session. It goes on to describe how the features
of Pathway/iTS help to maintain availability even if a critical application component
fails. Finally, this subsection indicates the issues related to application design that you
must consider to ensure that your application runs with high availability.
How Pathway/iTS Works
Figure 6-6 shows the major components of a Pathway/iTS application.
COBOL is a high-level language developed by HP for creating and running screen
programs, which are the programs that display and control data-entry and data-enquiry
screens on fixed-function terminals. By using the COBOL compiler to develop your
screen programs, you are able to simplify and standardize programming tasks, thereby
reducing the time and costs of those efforts. Because COBOL is based on COBOL,
application developers are able to learn and use COBOL quickly and easily.