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You can view historical data logged to a Citadel database in the following ways:

• Use the Historical VIs and the Historical Trend Express VI. You can specify the traces that the Historical Trend Express VI displays. You cannot browse to other traces, zoom in, jump to breaks, or jump to minimums and maximums in the display.
• Use the Historical Data Viewer. With the Historical Data Viewer, you can view any number of traces and browse to traces within multiple databases. You can zoom out to any width, locate breaks, and jump to minimums and maximums of a trace.
• Use an ODBC-compliant program to query the Citadel database.

Accessing Historical Data Using Historical Data VIs

Use the Historical VIs in a human machine interface (HMI) to retrieve and manipulate data logged in Citadel database files. You can use these VIs to browse files, extract the information in a format to display in the Historical Trend Express VI, or export the data to a spreadsheet file format.

Using URLs with Historical VIs

You can use URLs to locate data across a network with the Historical VIs. You can enter a URL from the front panel directly into a shared variable control. Right-click the shared variable control and select Allow Undefined Names from the shortcut menu.

The general form for the URL for shared variables is \\ComputerName\ProcessName\SharedVariableName, where ComputerName is the name of the computer running the process containing the SharedVariableName on the network, ProcessName is the name of the process containing the data item you want to connect to, and SharedVariableName is the name of the data item to which you want to connect.

Tip  Use \\localhost\ProcessName\SharedVariableName when you deploy an application to reduce the amount of modifications you have to make to the application if you move the application to a different computer.

You do not need to enter a path to the Citadel database. The LabVIEW Datalogging and Supervisory Control (DSC) Module can locate the Citadel database using the name of the computer on which the database resides and the database name. A database URL consists of the computer and database name where data for the source is stored, for example \\computer\my_database.

If you use a URL input for a variable name input in addition to a database URL for the database URL input with a Historical VI, the DSC Module checks the data directory specified by database URL for the shared variable part of the URL. If the DSC Module does not find that shared variable, it reports that it cannot access the shared variable. If you use a URL input for a variable name input while the database URL input is blank, the DSC Module uses the variable name URL to locate the shared variable data.

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