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Owning Palette: Historical VIs
Requires: DSC Module
Obtains the first and last timestamp available in the Citadel historical database for a given shared variable and the type of the shared variable: analog, bit array, discrete, string, or variant.
|timeout specifies the maximum time, in seconds, that this VI waits for reading data from the Citadel database. The default is 30. A timeout value of less than or equal to 0 specifies no timeout, which means this VI waits indefinitely until this VI receives data from the Citadel database.|
|database URL specifies the computer name and the database name where the Citadel database resides. Enter the database URL in the format \\computer\database. |
For example, if you have a copy of the LabVIEW Datalogging and Supervisory Control (DSC) Module and Citadel service installed on a computer named datalogger and the name of the database on that computer is data, you can access the data on datalogger from another computer by using the path \\datalogger\data. If you provide a database name only, this VI searches for the database on the local computer. If you do not wire database URL, this VI resolves the database URL from the Shared Variable Engine (SVE). If the SVE resolution fails, this VI reads data from the database associated with the default DSC Module process.
|trace name specifies the trace that this VI is using for the data operation. You can specify either a Shared Variable reference or an existing trace for this parameter. If the trace is not logged in the historical database, data type is set to Undefined and the first timestamp and last timestamp are set to 0.|
|error in describes error conditions that occur before this node runs. This input provides standard error in functionality.|
|data type is the type of shared variable. This VI returns Undefined if the shared variable is not logged in the Citadel database.
|database URL out returns the computer name and the database name that specify where the Citadel database resides. The format is \\computer\database.|
|first timestamp is the date and time associated with the first data point retrieved from the historical database.|
|last timestamp specifies the date and time associated with the last data point retrieved from the historical database.|
|error out contains error information. This output provides standard error out functionality.|