1. A system analysis program for analyzing an operational form of a network to which a plurality of servers are connected, by using a computer, said system analysis program makes the computer execute processing comprising the steps of: (a) collecting messages transmitted or received through said network by using a message monitoring unit; (b) analyzing contents of said messages collected in step (a), determining process types requested by said messages and whether or not each of the messages is a request message or a response message, and storing in a protocol-log storage unit as a protocol log information which indicates the determined process types, by using a message analysis unit; (c) identifying at least one process corresponding to each process type, based on at least one correspondence relationship between at least one request message and at least one response message corresponding to said each process type which are indicated in said protocol log stored in said protocol-log storage unit, generating a transaction model which satisfies 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 certainty of existence of caller-called relationships, and storing the generated transaction model in a transaction-model storage unit, by using a model generation unit when an instruction for generation of a model is inputted into the model generation unit; and (d) extracting from said protocol-log storage unit record items constituting said protocol log and conforming to at least one caller-called relationship indicated by said transaction model stored in said transaction-model storage unit, and analyzing a processing status of a transaction constituted by messages indicated by the extracted record items, by using an analysis unit when an instruction for analysis is inputted into the analysis unit.