Availability Guide for Application Design

What Is Application Availability?

Availability Guide for Application Design—525637-004

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Collecting Outage Data

For the next step towards increasing the availability of your application, you need to

establish the causes or potential causes of application outage. If you are designing a

new application, you should include the ability to collect outage data in your design.

You can analyze your data after some appropriate period of time. The outage data

should include information about all parts of the application and related system

software and hardware that are necessary to keep the application running. This

information should include not only the cause of the failure, but also its duration.

For existing applications, you can add the necessary logic to the application in order to

generate this information.

The first part of Figure 1-3 on page 1-24 shows the collection and distribution of outage

information provided by the system software that comes on a NonStop system. The

figure shows a typical client/server arrangement. EMS messages are generated on

behalf of system processes and saved in a central repository, $0. System problems in

the client are reported to a network management console.

The second part of Figure 1-3 on page 1-24 shows the collection and distribution of

outage information after you have added the errant information from the application

and gathered similar information from the client system. In addition, outage data is

added manually because this information cannot be automatically collected when the

system itself is down.

EMS provides the same framework for gathering application events as it does for

system events. Filters and collectors allow you to systematically extract events of

interest and forward them to a central repository for analysis with a tool such as the

EMS Analyzer.

Section 8, Instrumenting an Application for Availability, provides a general introduction

to instrumentation. The EMS Manual provides details of EMS. The Event Management

Service (EMS) Analyzer User’s Guide and Reference Manual tells you how to use the

EMS Analyzer.