Providing Open Architecture High Availability Solutions

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System model – A computer-usable representation of the capabilities, characteristics and

dependencies of all of the components that could be included in a system.

Temporal redundancy – Redundancy provided by re-performing operations. Most network

protocols provide this form of redundancy, as raw network traffic is inherently subject to errors.

Threshold crossing – This action occurs when the value of a particular parameter being monitored

crosses over a pre-determined point while either rising of falling. It is typically used to trigger a

fault detector, for example a high temperature in the chassis may be used to trigger a fault detector.

TMR – see Triple modular redundant

Triggered – Setting a fault detector from showing no fault to showing a fault. Triggering a fault

detector starts the process of fault management.

Triple modular redundant (TMR) – A redundant system in which there are three modules

operating in parallel. If they do not all give the same information an error is detected and the output

information is set to equal whatever two of the components agree upon.

Unassigned – The role of a redundant component that is not in standby, but is available to be

placed into service by the configuration management service. An unassigned component is the

same as a spare.

Value Coasting – Using a previous output value instead of a known bad value to avoid system

failure. This is a form of fault isolation, but it must be used with notification of the failure.

Verification – The process of checking a system to ensure that design or implementation issues

have not created latent faults.

Walk-over – An occurrence of one software component, or section of that component, over-

writing the memory allocated to another component. One typical example of this is stack overflow,

where the stack pointer start writing stack information on top of program code.

Warm Restart – Restarting a system without turning off the hardware.

WBEM – see Web-Based Enterprise Management.

Web-Based Enterprise Management (WBEM) – A standard being driven by the DMTF

(Distributed Management Task Force) for managing groups of computers connected in a network.