A system analysis program which can accurately analyze the operational status of a system without modifying functions of the system for providing services. A message analysis unit analyzes the contents of collected messages, and determines the times of occurrence of the messages, the process types requested by the messages, and whether or not each of the messages is a request message or a response message. In response to an instruction for model generation, a model generation unit generates a transaction model satisfying at least one limiting condition related to caller-called relationships between processes, based on a set of messages selected in accordance with a selection criterion based on the certainty of existence of caller-called relationships. Then, in response to an instruction for analysis, an analysis unit analyzes the processing status of a transaction based on a protocol log conforming to the transaction model.