Abstract An attempt to capture software aging and specify when to do preventive maintenance (PM) is presented in this paper. A composite measure termed the DRM,
Deteriorating Response Measure, is defined. It is based on the analysis of the deteriorating speed of the software against time and load. This speed is characterized as follows: (1) It decays with increased load. (2) It does not increase again when the load decreases, this indicates
loss of elasticity.
The DRM is mathematically formulated based on a queueing system model.
Specifying when to do preventive maintenance depends on the decision maker's perspective of the manifestation of aging. It is tried here to formalize this dependence. Three degrading performance metrics are defined for a DRM: (1) Decaying restored speed value. (2) Increasing speed offset ratio (recoverability index). (3) Increasing operation interval offset. These metrics can be used singly or aggregately in a DRM to specify when to do preventive maintenance. Results of model testing are also shown.
This work can be part of an on-line procedure that calculates performance indexes for a server type software system like a web browser, an operating system, a database, and helps in the decision to do preventive maintenance for aging software.
operational software systems - performance degradation - preventive maintenance - queueing model - software aging - system restoration