A computer program which causes a computer to perform a procedure comprising: capturing packets flowing over a network; reconstructing protocol messages from the packets to obtain transaction data (6, 6a, 6b) that records a plurality of transactions executed in a coordinated way by a plurality of servers (21 to 26) in a multi-tier system during a given analysis period, the transaction data (6, 6a, 6b) indicating execution periods of processes executed by the servers (21 to 26) in each tier of the multi-tier system; determining whether a response time of each transaction falls within an acceptable time range that is specified previously, based on the transaction data (6, 6a, 6b); dividing the given analysis period into a plurality of time windows and calculating, for each window, a load of the processes executed in parallel by the servers (21 to 26) in a specified tier, based on the transaction data (6, 6a, 6b) of the individual transactions, wherein the servers (21 to 26) in the specified tier have a throughput that increases along with an increase of the load and stops increasing when the load reaches a level; calculating, based on the transaction data (6, 6a, 6b) of the transactions whose response times are determined to fall within the acceptable time range, a throughput in each time window of the processes executed, as part of the transactions whose response times are determined to fall within the acceptable time range, by the servers (21 to 26) in the specified tier during said each time window; determining, based on the calculated load and throughput of each time window, a first load value as a first threshold at which the throughput begins to decrease in spite of an increase of the load; determining, based on the calculated load and throughput of each time window, a second load value as a second threshold at which a ratio of an increase of the throughput to an increase of the load begins to fall below a specified value; and configuring the servers (21 to 26) in the specified tier with an allowable limit of concurrent processes, such that the load of the servers (21 to 26) falls within a range delimited by the first threshold and second threshold even when the servers (21 to 26) are loaded with as many concurrent processes as the allowable limit. capturing packets flowing over a network; reconstructing protocol messages from the packets to obtain transaction data (6, 6a, 6b) that records a plurality of transactions executed in a coordinated way by a plurality of servers (21 to 26) in a multi-tier system during a given analysis period, the transaction data (6, 6a, 6b) indicating execution periods of processes executed by the servers (21 to 26) in each tier of the multi-tier system; determining whether a response time of each transaction falls within an acceptable time range that is specified previously, based on the transaction data (6, 6a, 6b); dividing the given analysis period into a plurality of time windows and calculating, for each window, a load of the processes executed in parallel by the servers (21 to 26) in a specified tier, based on the transaction data (6, 6a, 6b) of the individual transactions, wherein the servers (21 to 26) in the specified tier have a throughput that increases along with an increase of the load and stops increasing when the load reaches a level; calculating, based on the transaction data (6, 6a, 6b) of the transactions whose response times are determined to fall within the acceptable time range, a throughput in each time window of the processes executed, as part of the transactions whose response times are determined to fall within the acceptable time range, by the servers (21 to 26) in the specified tier during said each time window; determining, based on the calculated load and throughput of each time window, a first load value as a first threshold at which the throughput begins to decrease in spite of an increase of the load; determining, based on the calculated load and throughput of each time window, a second load value as a second threshold at which a ratio of an increase of the throughput to an increase of the load begins to fall below a specified value; and configuring the servers (21 to 26) in the specified tier with an allowable limit of concurrent processes, such that the load of the servers (21 to 26) falls within a range delimited by the first threshold and second threshold even when the servers (21 to 26) are loaded with as many concurrent processes as the allowable limit.