Advise points

Advise points are sent to PI Interface for OPC DA by the OPC server only when a new value is read into the OPC server cache. Scan class 1 is reserved for advise points, and you can create additional scan classes for advise points as required. Ensure that the scan class rate is fast enough to capture all the changes from the data source. If assigned to scan class 1 (Location4 =1) , the interface assigns the tags to OPC groups with a default of 800 tags per OPC group. For best performance, ensure that your OPC group size does not exceed 800 items per group.

Note: Your server might perform better with smaller group sizes; a limit of 200 points per group has proven effective with a number of OPC servers.

To change the default limit for advise-based PI points in a scan class, use PI ICU to set the Number of Tags in the advise group field on the OPCInt > Data Handling page.

Configure the following PI point attributes to create advise points:

• location3

  Set to 1 for advise points.

• location4

  Assigns the scan class for a point; scan class 1 is reserved for advise points.

  Note: Do not assign the same scan class to both advise and polled points. Use a separate class for each point type.