1. A method of managing a computing system, including the steps of: generating transaction requests in accordance with a transaction profile of the system, said transaction requests being provided for processing by the system; collecting status data of a set of managed resources of the system in accordance with a system model stored in a knowledge base; determining performance indicators of the system from the status data in accordance with said system model; monitoring transaction performance of the system by comparing the performance of the system in processing said transaction requests with an expected performance; and when a degradation in transaction performance is detected, generating a signal to indicate that a degradation in performance has occurred, to enable the status data and/or performance indicators to be analysed at the time at which said performance degradation occurs.