The present invention provides a technique for improving the reliability of access to a database system in a controller, such as a PLC. A PLC accessible to a database accesses a DB server in response to an event in which a user program calls a DB access processing program. The DB access processing program stores status information indicating a status of accesses to the DB server in a nonvolatile memory, in accordance with an instruction of the user program. When a power interruption occurs, the PLC can obtain a status of accesses to the DB server at the timing of the occurrence of the power interruption by referring to the status information. Then, the PLC, for example, re-sends a SQL sentence, depending on the access status.