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Availability Management

Availability Management is the practice of identifying levels of IT Service availability for use in Service Level Reviews with Customers / Clients.

All areas of a service must be measurable and defined within the Service Level Agreement (SLA). To measure availability the following areas are usually included in the SLA itself:

  • Agreement statistics: such as what is included within the agreed service.
  • Contingency: agreed contingency details, location of documentation, contingency site, 3rd party involvement, etc.
  • Capacity: performance timings for online transactions, report production, numbers of users, etc.
  • Help Desk Calls: number of incidents raised, response times, resolution times.
  • Availability: agreed service times, response times, etc.
  • Costing Details: charges for the service, and any penalties should service levels not be met.


Availability is usually calculated based on a model involving the Availability Ratio and techniques such as Fault Tree Analysis, and includes the following elements:

  • Serviceability: where a service is provided by a 3rd party organisation, this is the expected availability of a component.
  • Maintainability: the ease with which a component can be maintained, which can be both remedial or preventative.
  • Resilience: the ability to withstand failure.
  • Reliability: the time for which a component can be expected to perform under specific conditions without failure.
  • Recoverability: the time it should take to restore a component back to its operational state after a failure.
  • Security: the ability of components to withstand breaches of security.



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