| 摘要 |
A process control system has a network which includes a plurality of modules, each module performing a predetermined function. The modules include at least one history module, and at least one application module, the modules being linked via a medium such that each module can communicate with every other module of the network. The network interfaces with a control subsystem which interfaces with control elements of a plant process, the control elements having associated therewith process data. The process data includes data values and event data; the total data includes process data, data calculated from the process data, off-line data, and external data, the total data being stored in a storage device of the history module. A method for maintaining the total data comprises the steps of queuing messages requesting selected portions of the total data to be stored in said storage device. The next step is processing the messages to determine if a new record is to be written in the storage device, and if a new record is to be written, proceeding to the next step; otherwise, skip to the updating step. The next step is that of writing the new record in a next available adjacent record of the storage device, and then repeating the processing, beginning with the queuing step. In the updating step, the record requested via the message is updated with the selected portions of the total data as specified by the message. Finally, the processing is repeated beginning at the step of queuing.
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