A programmable controller includes a command execution unit that executes multiple commands in a user program in order; a database storage unit that stores therein a database that holds data used in a process performed by the command execution unit in a table format; a database-query-command generation unit that, when the commands include a command to access the database, converts the access command into a database query command described in a database query language; and a database management unit that accesses the database in the database storage unit and acquires data specified by the database query command.

A controller for controlling a control object includes a communication interface, an instruction executor, and an access processor. The communication interface accesses a database device. The instruction executor executes a user program including an access instruction for accessing the database device, the user program being associated with control of the control object. The access processor generates an access request in response to execution of the access instruction and causes the communication interface to transmit the access request. The access processor extracts an access request satisfying a prescribed condition from an error list including access requests recorded when access to the database device fails and causes the communication interface to retransmit the access request extracted.

A controller performs a control operation associated with a control target. The controller includes a communication interface that electrically connects at least one function unit to the controller through a data transmission path, a writing unit that writes an observation value obtained through the function unit into a database, and a delay obtaining unit that obtains a delay time taken from when a signal indicating an observation value is input into the function unit to when data representing the observation value becomes usable in the controller, and stores information indicating the obtained delay time.

A controller performs a control operation associated with a control target. The controller includes a communication interface that electrically connects at least one function unit to the controller through a data transmission path, a writing unit that writes an observation value obtained through the function unit into a database, and a delay obtaining unit that obtains a delay time taken from when a signal indicating an observation value is input into the function unit to when data representing the observation value becomes usable in the controller, and stores information indicating the obtained delay time.

A controller for controlling a control object includes a communication interface, an instruction executor, and an access processor. The communication interface accesses a database device. The instruction executor executes a user program including an access instruction for accessing the database device, the user program being associated with control of the control object. The access processor generates an access request in response to execution of the access instruction and causes the communication interface to transmit the access request. The access processor extracts an access request satisfying a prescribed condition from an error list including access requests recorded when access to the database device fails and causes the communication interface to retransmit the access request extracted.