Availability Guide for Application Design

Contents
Availability Guide for Application Design—525637-004
v
7. Instrumenting an Application for Availability
6. Availability in the Pathway Transaction-Processing
Environment (continued)
Summary and Comparison of Application Components 6-28
7. Instrumenting an Application for Availability
Design Philosophy for Error Handling 7-2
Checking for Errors 7-2
Writing Code to Handle Problem Errors 7-4
What Is Instrumentation and Why Is It Necessary? 7-7
Why Is Instrumentation Necessary? 7-7
How Does Instrumentation Improve Availability? 7-8
A Framework for Planning and Developing Your Instrumentation 7-10
Who to Notify? 7-14
Automating Object Management 7-15
Alternatives to DSM 7-16
Advantages of DSM 7-16
Overview of DSM Architecture 7-17
The Subsystem Programmatic Interface (SPI) 7-19
The DSM Subsystem Environment 7-25
DSM Management Services 7-31
The Operations Environment 7-36
Availability Requirements of DSM Management Applications 7-36
User-Written Management Applications 7-38
DSM Management Tools and Performance Measuring Tools 7-40
8. Availability Through Process-Pairs and Monitors
When to Use Process Pairs 8-2
Approaches to Takeover
8-3
Operations That Are Retryable
8-3
Operations That Are Not Retryable 8-4
How Do Process Pairs Work? 8-4
Passive Backup Model 8-6
Starting the Passive Backup 8-6
Sending Process-State Information to the Passive Backup 8-6
Receiving Information in the Passive Backup 8-8
Takeover by the Passive Backup 8-10
Active Backup Model 8-12
Starting the Active Backup 8-12
Sending Process-State Information to the Active Backup 8-13