The OPC branch of the Server Status Tool includes an XML-DA Items category. The category provides status information about the XML-DA tags to which XML-DA clients are subscribed. Status information is shown for XML-DA tags when XML-DA is used to access the database. Each XML-DA tag represents a path to a value for an item.
The status information for each XML-DA tag is categorized as:
- Tag—Indicates the name and location of the XML-DA tag to which the XML-DA client subscribes.
- Subscription—Indicates the name of the subscription being used for retrieving data from the server. You can view status information about the subscriptions on the status display for XML-DA Subscriptions.
- Update Count—The count of changes that Geo SCADA Expert has detected and sent to the client since the most recent one of these activities occurred:
The client subscribed to the tags
The last snapshot (if the Reset Counters check box is selected in the Snapshots section of the Server Configuration Tool)
A manual reset was triggered via the context-sensitive menu (see the Reset option described below).
The count is incremented for changes to the value or quality.
- Last Update—The time that Geo SCADA Expert detected the last change and queued that change, ready to send it to the client. This is not the time that the point value changed; it is the time that the interest thread detected the change, which may be a little bit later than the point value change.
- Canonical Data Type—Shows the original type of the OPC data that is being requested. This can be:
- VT_BSTR—a string value
- VT_BOOL—a Boolean value
- VT_VARIANT—the type varies (and can be any of the other data types)
- VT_I1—a 1 byte signed integer value
- VT_I2—a 2 byte signed integer value
- VT_I4—a 4 byte signed integer value
- VT_UI1—a 1 byte unsigned integer value
- VT_UI2—a 2 byte unsigned integer value
- VT_UI4—a 4 byte unsigned integer value
- VT_R4—a single precision floating value
- VT_R8—a double precision floating value
- VT_DATE—a date and time value.
These data types can also be arrays, in which case, the data type is appended with |VT_ARRAY, for example, VT_UI4|VT_ARRAY.
- Requested Data Type—Shows the data type that has been requested (some OPC clients can request data in a different type to that in which it stored in the Geo SCADA Expert database, for example, a real value could be requested as a string).
The data types that can be requested are:
- VT_EMPTY—A value has not been specified. This means that the client has not requested for the value to be converted from its original data type. The data type of the value that is returned will be the same as the value’s Canonical Data Type.
- VT_I1—a 1 byte signed integer value
- VT_I2—a 2 byte signed integer value
- VT_I4—a 4 byte signed integer value
- VT_R4—a single precision floating value
- VT_R8—a double precision floating value
- VT_CY—a currency (monetary) value
- VT_DATE—a date and time value
- VT_BSTR—a string value
- VT_BOOL—a Boolean value (True =-1, False=0)
- VT_UI1—a 1 byte unsigned integer value
- VT_UI2—a 2 byte unsigned integer value
- VT_UI4—a 4 byte unsigned integer value.
These data types can also be arrays, in which case, the data type is appended with |VT_ARRAY, for example, VT_UI4|VT_ARRAY.
Totals
When the XML-DA Items category is populated with entries, a Totals row is added to the bottom of the list of entries.
The Totals row indicates the total number of rows (excluding the Totals row), along with the total Update Count of all of those rows.
You can access a context-sensitive menu by right-clicking on an entry in the list. The menu has this option:
-
Reset All Update Counts—Use to reset all of the update counts and last update times.
If the Reset Counters check box is selected on Server Snapshot Log files, the counts will also be reset whenever a snapshot is taken (see Server Snapshot Log Files in the Geo SCADA Expert Guide to Server Administration).