Availability Guide for Change Management

Introduction to Change Management

Availability Guide for Change Management–125506

1-6

Reducing the Time Required for Planned Outages

An outage is time during which your NonStop system is not capable of doing useful

work. From the end-user’s perspective, an outage is any time an application is not

available.

Outage Classes

Outages fall into the following classes:

•

Physical

•

Design

•

Operations

•

Environmental

•

Reconfiguration

Unplanned Outages

The first four industry-standard outage classes describe unplanned outages. An

unplanned outage is system or application downtime caused by a problem such as faulty

hardware, operator error, disaster, and so forth. Unplanned outages—and how to

predict, prevent, and prepare for them—are described in the Availability Guide for

Problem Management.

Planned or Reconfiguration Outages

The reconfiguration outage class includes all planned outages. A planned outage is

system or application downtime that is planned or scheduled.

A reconfiguration outage might occur for an incremental reconfiguration, such as adding

a disk or a communication line, or for massive reconfiguration, such as migrating from a

complex instruction set computing (CISC) system to a reduced instruction set computing

(RISC) system, from a C-series operating system release to the D-series, or from one

version of an application to another.

Your NonStop system is designed so that most changes can be performed while the

system and applications are still operational. However, certain changes must be done

offline. Offline change is any change that requires your NonStop system to be shut

down. Offline changes—as well as online changes that affect application availability—

are the typical causes of planned outages.

Section 2, “Change Control,” explains how you can ensure that planned outages proceed

smoothly by establishing a formal change-control process. Section 6, “Reducing the

Time Required for Planned Outages,” describes several techniques you can use to reduce

the time required for planned outages.

Measuring Outages

Tandem believes that the measurement of availability should be from the end-user’s

perspective. For example, it is not enough simply to record that a certain hardware or

software component has gone down; you must also take into consideration the user’s