Effective fault treatment for improving the dependability of COTS and legacy-based applications

This paper proposes a novel methodology and an architectural framework for handling multiple classes of faults (namely, hardware-induced software errors in the application, process and/or host crashes or hangs, and errors in the persistent system stable storage) in a COTS and legacy-based application. The basic idea is to use an evidence-accruing fault tolerance manager to choose and carry out one of multiple fault recovery strategies, depending upon the perceived severity of the fault. The methodology and the framework have been applied to a case study system consisting of a legacy system, which makes use of a COTS DBMS for persistent storage facilities. A thorough performability analysis has also been conducted via combined use of direct measurements and analytical modeling. Experimental results demonstrate that effective fault treatment, consisting of careful diagnosis and damage assessment, plays a key role in leveraging the dependability of COTS and legacy-based applications.