1. A computer-readable, non-transitory medium storing the system analysis program, said system analysis program makes the computer execute processing comprising: collecting a message transmitted or received through said network; analyzing contents of said collected message; determining a process type requested by said message and whether or not the message is a request message or a response message; storing the message in a protocol-log storage unit as a protocol log information which indicates the determined process type; identifying at least one process corresponding to the determined process type based on a correspondence relationship between a request message and a response message corresponding to the process type which is indicated in said protocol log when receiving an instruction for generating a model; generating a transaction model which satisfies a limiting condition related to caller-called relationships between processes, from a set of messages selected in accordance with a selection criterion based on certainty of existence of caller-called relationships, the transaction model containing a list of messages to be transmitted until a completion of a transaction; storing the generated transaction model in a transaction model storage unit; extracting from said protocol-log storage unit a record item of said protocol log conforming to a caller-called relationship indicated by said transaction model stored in said transaction-model storage unit when receiving an instruction for analyzing; and analyzing a processing status of a transaction constituted by a message indicated by the extracted record item, wherein when there are a plurality of processes which are possible to call a process to be called, the generating uniformly determines a probability of a call from each of the plurality of processes, integrates probabilities of calls from the plurality of processes to other processes into probabilities on a process type basis, and calculates the likelihoods of caller-called relationships.