In addition to logging data using shared variables, you can manually log data to Citadel using the Database Writing VIs. You can use these VIs to add data with a specific timestamp. This type of operation is useful when using OPC servers that maintain relatively constant values. OPC servers send data only when the value changes. Therefore, you can update the value timestamps by writing periodically to the database using the VIs shown above.
Because the Shared Variable Engine has to make determinations about which data to log, and when, writing directly to Citadel is more efficient. Data is written directly to the Citadel Service, not routed through the SVE.
Refer to the Database Direct Write Demo.lvproj in the labview\examples\lvdsc\Data and Alarm Historical Logging\Database Direct Write Demo directory for an example of using the Write Trace VI.
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