OPC DA servers

Add OPC DA server

With the OPC DA Servers navigation node selected, click on the “Add” button to add a new OPC DA server.

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This will open a dialog to prompt for OPC DA server details.

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( 1 ) Enter the host name where the OPC DA server is installed.

( 2 ) Enter the “Prog ID” or “GUID” of the OPC DA server. When you click on the entry field then the OPC DA connector will attempt to automatically offer a selection of available OPC servers.

( 3 ) Once the Prog ID or GUID has been entered, the “Add” will be enabled. Click on the button to add the OPC server.

Remove OPC DA server

If you no longer wish to use an OPC DA Server that you have previously added then select the OPC DA Servers navigation node (1), the OPC DA Server you wish to remove (2) and click on the “Remove” button (3).

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Warning

Note that all topics configured for the OPC DA server will be also be removed. This affects all tasks using these topics.

Reassign OPC DA server

Reassign the OPC DA Server to change the host of the OPC DA server. Select an OPC DA Server in the content panel, then use the “Reassign” button in the toolbar to reassign the OPC DA Server. Reassignment takes effect when the next session with the OPC DA server is established.

Note

Running tasks and live value views keep existing sessions alive. Turn off live values or do not view live values and wait for 15 seconds to ensure that live value viewing sessions are released. Finally, stop and re-start tasks that use the OPC DA server. Right-clicking on the OPC DA server in the navigation panel and selecting “Reinitialize” will restart sessions immediately.

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Redundancy

Client-side OPC DA Server redundancy management is available in the OPC DA Connector as a preview feature. “Client-Side” means that redundancy is managed by the OPC DA connector without any supporting functionality on the OPC DA server side.

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To configure redundancy, add two OPC DA servers to your configuration, for example, one called “Server 1” (the primary server) and another one called “Server 2” (the secondary server). The backup server should be hosted on a different computer; the OPC DA server type and server-side configuration (including any required credentials) should be the same.

On the Dataristix side, add topics and tags to the primary server only. The secondary server does not require any topics or tags configured and can remain “empty”.

The following settings are available:

  • Secondary Server

    The server that should be used as a backup.

  • Trigger condition

    • Switch over when the OPC server connection is lost.

      The OPC DA connector changes connections (from primary to secondary or vice versa) when a connection to the current OPC server is lost.

    • Switch over when the OPC server connection is lost or when the trigger tag’s status is not ‘good’.

      The OPC DA connector changes connections (from primary to secondary or vice versa) when a connection to the current OPC server is lost or when the trigger tag’s status it not ‘good’. See below for an explanation of ‘trigger tag’.

    • Switch over when the OPC server connection is lost or when the trigger tag’s value is ‘False’ or equal to zero.

      The OPC DA connector changes connections (from primary to secondary or vice versa) when a connection to the current OPC server is lost or when the trigger tag’s value evaluates to ‘False’. A switch-over is only initiated if the trigger tag’s status is ‘good’. The tag value is first converted to boolean before evaluation. A numerical value of zero evaluates to ‘False’ and a non-zero value evaluates to ‘True’. A string-type trigger tag evaluates to ‘False’ if the string is empty, to ‘True’ otherwise. See below for an explanation of ‘trigger tag’.

    • Switch over when the OPC server connection is lost or when the trigger tag’s value is ‘True’ or not equal to zero.

      The OPC DA connector changes connections (from primary to secondary or vice versa) when a connection to the current OPC server is lost or when the trigger tag’s value evaluates to ‘True’. A switch-over is only initiated if the trigger tag’s status is ‘good’. The tag value is first converted to boolean before evaluation. A numerical value of zero evaluates to ‘False’ and a non-zero value evaluates to ‘True’. A string-type trigger tag evaluates to ‘False’ if the string is empty, to ‘True’ otherwise. See below for an explanation of ‘trigger tag’.

    • Switch over when the OPC server connection is lost or when the trigger tag’s value equals the trigger value.

      The OPC DA connector changes connections (from primary to secondary or vice versa) when a connection to the current OPC server is lost or when the trigger tag’s value equals the configured trigger value. A switch-over is only initiated if the trigger tag’s status is ‘good’. The tag value is first converted to string before comparing to the configured trigger value. If values match, then a switch-over is initiated. See below for an explanation of ‘trigger tag’.

    • Trigger Topic

      The trigger topic is the topic that contains the trigger tag (see below) and needs to be defined for trigger conditions involving a trigger tag. It is recommended that a dedicated topic is created for the primary OPC DA server, containing just the trigger tag. The topic must not be ‘Write Only’. The topic’s read rate and read mode determine how and how frequently the trigger tag is monitored for changes.

    • Trigger tag

      The trigger tag is a tag within the trigger topic and needs to be defined for trigger conditions involving a trigger tag. The tag’s value or status may be evaluated to effect a switch between primary and secondary OPC DA server (or vice versa).

    • Trigger value

      Enter a trigger value if the selected trigger condition involves a trigger value comparison (see above).

Use the “Clear All” button to clear all settings including trigger topic and tag references. You will need to clear tag references before you can delete trigger topics and trigger tags from the OPC server.

Apply changes to update settings. Changes take effect when the next session with the primary OPC DA server is established.

Note

Running tasks and live value views keep existing sessions alive. Turn off live values or do not view live values and wait for 15 seconds to ensure that live value viewing sessions are released. Finally, stop and re-start tasks that use the OPC DA server. Right-clicking on the OPC DA server in the navigation panel and selecting “Reinitialize” will restart sessions immediately.