Maintainability: The ability of an IT component to remain in, or be restored to an operational state.Serviceability: The ability for an external supplier to maintain the availability of component or function, whether or not under a third-party contract.A good example of Maintainability is a computer system from the ’90s where the serial numbers onthe computers were important for maintaining the computers, but the serial numbers were placedsuch that a machine had to be disassembled to see it. These systems were not designed withserviceability in mind.A good example of Serviceability is in the aircraft industry. Often, changing a light bulb over apassenger seat requires a maintenance person. Design engineers have finally started to make theselights easy to service so that anybody could change the light bulb, increasing the serviceability of theaircraft.Resilience: A measure of freedom from operational failure and a method of keeping services reliable. How capable is the system to withstand problems?One popular method of resilience is redundancy.A good example of Resilience was the U.S. space shuttle, which had a "fly by wire" control system.This means that the pilot’s commands were sent to an onboard computer which then controlled thespacecraft. With a system like that, the resiliency of the shuttle’s computer is critical to both itssuccessful operations and to staying alive! Therefore, the space shuttle had multiple computersoperating in parallel in case of a failure. This is hardware redundancy. Another availability risk is in thesoftware for these systems. What if all the machines hit the same software bug at the same time? Toaddress this risk, system engineers used redundancy again, creating two independent code bases forModule 3...12 of 172/4/2019, 8:41 PM
the computers. Different code bases ran on the different, parallel computers to minimize risk if oneshould fail.Security: A service typically will have associated data. Security refers to the confidentiality, integrity, and availability of that data.MetricsAvailability should be measured quantitatively with the measures and their targets being determined based on the operational requirements of the healthcareorganization. One example is Beth Israel Deaconess Medical Center (BIDMC) in Boston. BIDMC has service level requirements for application systems. BIDMCdefines four levels of applications based on their requirements for availability.Availability Management Metrics–Beth Israel Deaconess Medical Center (BIDMC)John Halamka Blog, June 3, 2009Customer Availability Objectives: These objectives are determined by the BIDMC IS Help Desk Manager working with the Customer/Subject Matter Expert (SME)and are based on the customer/SME’s stated “Downtime Tolerance and Response Expectations” specified in the IS Support Services Service Level Agreement(SLA). The customer Availability Objectives are intended to correspond with the IT Disaster Downtime and Recovery Classifications below. (Halamka, 2009)
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