Availability Guide for Application Design

Availability in the Pathway Transaction-Processing
Environment
Availability Guide for Application Design—525637-004
6-28
Summary and Comparison of Application
Components
Operational Concerns
Consider the following operational issues when designing a highly available TCP
application:
•
Consider whether the TCP should be run as any of the following:
°
A process pair with continual checkpointing
°
An initialized persistent process
°
An immediately persistent process
or whether it should be run without any of these features.
•
If you decide to run your TCP as a single process without any availability features,
then operations staff must take the responsibility for getting a failed TCP restarted.
Manually restarting the TCP clearly implies a lower level of availability if a failure
occurs than you would get though process persistence or process pairs.
•
If you choose to rely on operator restart to recover from a stopped TCP, a well-
instrumented application can speed up recovery by bringing the stopped process
to the immediate attention of an operator or can even help 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.
Summary and Comparison of Application
Components
Table 6-1 on page 6-29 and Table 6-2 on page 6-29 show the recovery techniques
used with the various components described in this section that make up a Pathway
application. They show whether a specific technique is used to enhance the availability
of a given process type. They indicate whether the technique applies automatically,
whether it is automatic if so configured, whether it is up to the developer to provide the
feature by writing additional code, or whether it depends on the function of the
workstation. Specifically, the entries in Table 6-1 and Tabl e 6-2 on page 6-29 have the
following meanings:
•
Automatic
The technique is automatically applied to keeping that entity online. It is not
necessary for the developer to do any additional coding for the feature, nor is it
necessary to perform configuration or other operational activity.
•
Configurable
The technique is applied to the entity if the entity is so configured. No application
coding is necessary.
•
Development responsibility