PURPOSE: To eliminate necessity for preparing plural data bases for a data base update test and further to use the initialized data base for plural jobs at the same time.

CONSTITUTION: File pseudo caches 3-1 to 3-n for holding the copy of one part of a data base 1 are provided in a respective test groups 2-1 to 2-n composed by combining plural job programs P. When the update of the data base is requested from the job programs P inside the test groups 2-1 in 2-n and the requested data are existent in the correspondent file pseudo caches 3-1 to 3-n, a file access managing mechanism 4 performs the update operation on the same caches 3-1 to 3-n, when those data are not existent, the update operation is performed on the same caches 3-1 to 3-n after the data are copied to the caches 3-1 to 3-n, and the update operation is not performed on the data base 1 in both of cases.