Providing Open Architecture High Availability Solutions

components in the system (dependencies) and the conversions of any data storage that may need to

be updated as well. Also, a software upgrade should include a rollback feature that allows the

system to be returned to the original operation prior to the upgrade.

Diagnostics are tools for verification. The final step in the repair action is to be sure that the new

component is working properly.

6.5.5 Techniques

Component Replacement. This technique includes physical replacement of the failed component.

Debug and Diagnostics. Before a component is removed from a system diagnostic and debug

utilities may be used to find the atomic component that has faulted within the component. These

techniques are also used just after a component is placed back into a system to verify that the

component works correctly.

Off-line diagnostics are typically provided by the manufacturer of the component. A method needs

to be in place to connect an off-line component to an alternate input and output stream in order to

run the diagnostics.

When off-line diagnostics are complete, the information about the diagnostics (including time,

version, results, etc.) should be stored in the system information data block for that component

and/or its subcomponents.

Software Patching. This technique involves replacing pieces of a software component. The desire

would be to do this while the component is being used. A residual signature is needed to show that

a patch has been applied. A mechanism to remove the patch and its associated signature must also

be provided.

Software Upgrade. This technique involves the replacement of the component and dependent

components in the system. The operation should be performed while the system is providing

service but will normally take some level of switchover action and conversion action after the

installation is complete.

6.5.6 Dependencies

The repair action depends on the manual actions of the craftsperson. This is the most error-prone

item and the system must be prepared to expect the unexpected. Other dependencies include

component identification and versioning, and diagnostics.

6.6 Notification

6.6.1 Introduction

Components within a system must interact with each other to enable fault management.

Notification of fault information and the progression of the fault management process may occur

through various communication interfaces. For purposes of fault management, the notification

function focuses only on communication capabilities and interfaces between the fault management

processes and the fault communication between the layers.

This function builds upon the concept of system component interfaces (Section 5.4), and

management interfaces (both internal and external) that are detailed in Section 5.5.