Configure server-specific OPC watchdog points for efficient failover

OPC servers track their own states (isolated mode). To enable PI Interface for OPC DA to determine the state of an OPC server before attempting to failover to it, configure both OPC servers to track each other’s state as well (server-specific mode). This configuration enables the OPC server to determine the state of both servers without the overhead of creating a second connection.

Note: The method by which an OPC server tracks its state is highly vendor-dependent and implementations vary. For details, consult your OPC server documentation.

Use PI ICU to configure OPC watchdog points.

1. In both OPC servers, create identical items that track the status of each server.

   If an OPC server is active, the OPC item must contain a positive value. If an OPC server is unable to serve data, the item value must be zero. Implement any logic required to ensure that both servers correctly detect and maintain the status of the other server and that, in both OPC servers, the values are identical.

2. Configure the OPC servers so that, during normal operation, one server sends data to PI Interface for OPC DA and the other waits until the primary server fails.

   Status for the primary server must be positive, and for the backup server, status can be zero. If failover occurs, the primary server status must be set to zero and the backup server status to a positive value.

3. In Data Archive, create a watchdog PI point for each OPC server, mapped to the OPC items that track server status.

4. Using PI ICU, go to the OPCInt > Failover > Server Level page and set the Primary Server Watchdog Tag and Backup Server Watchdog Tag fields to the names of the watchdog PI points you created in the previous step.

   In the interface batch startup file, these settings are specified by the wd1 and wd2 parameters.

If both watchdog points are zero, data collection stops until one watchdog point becomes positive. If both watchdog points are positive, the interface remains connected to the server that is currently serving data to it.