Configure failover

You can specify that your InTouch application switches to a failover secondary I/O Server when it can no longer communicate with the primary I/O Server.

When you set the failover, you specify the failover deadband. The failover deadband is the delay in seconds before switching from the primary Access Name to the secondary Access Name. The InTouch HMI triggers the failover when the expression or an I/O communication failure is true for the length of the deadband period. When the failover deadband is set to 0 or blank, the failover is triggered as soon as an I/O communication failure is detected.

Configure failover for an Access Name

1. If needed, stop WindowViewer.

2. On the Home menu, in the Tags group, select Access Names.

   The Access names dialog box appears with a list of all defined Access Names.

3. Select the Access Name from the list to add a failover server.

4. Select Edit.

   The Add access name appears.

5. In the Secondary source section, select the Enable Secondary Source checkbox.

6. Do the following:

   • In the Node Name box, type the node name of the secondary I/O Server.

   • In the Application Name box, type the program name of the secondary I/O Server program from which data will be acquired.

   • In the Topic Name box, type the topic name you want to access from the secondary I/O source.

   • In the Which protocol to use area, select either DDE or SuiteLink as the secondary I/O Server communication protocol.

   • In the When to advise server area, select Advise all items or Advise only active items for the secondary I/O source.

7. In the Failover section, select the Enable failover checkbox.

8. Do the following:

   • Enter an optional failover expression or double-click in the Failover expression box to select a tag. For more information about failover expressions, see Force failover to a backup Access Name.

   • In the Failover Deadband box, type the length of the failover deadband in seconds.

   • Select Switch back to primary when Failover conditions clear if you want to enable switching from the secondary Access Name back to the primary Access Name after the failover condition clears.

     The default is to not switch back to the primary Access Name. If you select Switch back to primary when failover conditions clear, then the Fail-back Deadband option becomes selectable from the Failover Configuration dialog box.

   • From Failback Deadband, type the length of the failback deadband in seconds.

     The InTouch HMI triggers a failback to the primary Access Name after the expression and any associated I/O communication failure clear for the deadband period. When the expression is left blank or 0, the fail-back occurs as soon as the I/O communication failure condition clears.

9. Select Update.