PURPOSE: To shorten the response time of an on-line transaction processing program by providing a transaction processing program resident deciding means and a transaction processing program resident/nonresident changing means.

CONSTITUTION: The system has a transaction processing program resident deciding means 1, a transaction processing program resident/nonresident request means 2, a transaction processing program using condition counting means 3, a transaction processing program resident/nonresident changing means 4, a real memory control part 5, an executing program file (RU)6, a changing page evacuating file (BS)7, an executing program file linking information table 8 and a real memory resident deciding control table 9. Thus, an over-head due to a physical input from the executing program file RU6 with a page absent fault (MPF) to occur at the transaction executing process as a turning point, depending upon an occasion, a physical input output to a changing page evacuating file BS7 can be suppressed.