Data sources

Use the Data Sources dialog box to configure one or more data sources for a Trend Control object.

Access the dialog

To access the Data Sources dialog box for a specific Trend Control object, first access the Object Properties dialog for that object and then click Data Sources.

The dialog box in detail

The data source defines the location of the values from the data point(s) associated with it. Many points can share the same data source — you do not need to create one data source for each data point.

The data source tag is available by default to the Trend Control object. You can add additional data sources with the New button. The name you enter will be used as an alias to link the data points to this new data source.

For more information about adding data sources, see:

• Using the Data Source Database

The other fields in this dialog allow you to edit the data source settings:

Source Type

Select the source type of the location of the data point values. For more information about the different types of sources, see the table below.

X Axis field

If the X axis of the trend graph is set to be numeric instead of date/time (in the Axes settings), then enter the name of the field (column) of the data source that holds the data for the X axis.

Note: If you have enabled decimation (either in the Advanced settings for all trends or in the Options settings for a single trend), then the field that you have specified here must be sorted in ascending order. The procedure to do this varies by source type (for example, text editor, spreadsheet application, external database, etc.), so for more information, see the documentation for your specific type.

Max. Buffer

The maximum amount of data (in bytes) that will be held in runtime memory.

Load Progress

The tag in this field will receive a real value (0-100) that represents the percentage of the Data Source load progress.

Ann. Source

The name of the database table that contains text and image annotations to be displayed in the trend control. This must be a table in the same database that is configured to be the trend control's data source. Annotations are not supported for other types of data sources. For more information, see Display text- and image-based trend annotations in a trend control.

Sort

This option is useful for plotting data from a text file. When enabled (checked), it sorts the data and shows the Cursor column value until the Max. Buffer is filled. When disabled (unchecked), the data are not sorted and the Cursor column value is not shown.

Keep Open

This option keeps the data source open as long as the screen that contains the Trend Control object is open. This improves the performance of the runtime project, but keeping the data source open may cause other problems like database connection errors (when Source Type is Database) and file write conflicts (when Source Type is Batch or Text File). To close the data source after the data has been loaded, clear (uncheck) this option.

Data Source Settings

Click to define the settings for the selected Source Type

The following table summarizes the settings for each Source Type:

Note:

There is a default query timeout of 120 seconds, to prevent the project client from hanging on an unusually long data source query. To adjust the timeout period, manually edit your project file (<project name>.APP) and change the following setting:

[Trend]

QueryTimeout=120

If you change the value to 0, then there will be no timeout at all; data source queries will always continue until they are completed.