Continuation Point - Data Restriction per Client request or on Server side

This article is relevant for all .Net products

Some OPC UA services (e.g. HistoryRead to retrieve historical values from a variable) allow clients to restrict the maximum number of results per request. If a server has more results to deliver, it returns a continuation point along with the results which the client can use to request more results. A server application must be able to deliver the remaining result with context information stored within a continuation point.

Browsing the Address Space
OPC UA provides the services Browse and BrowseNext to browse the address space of a server. Browsing the address space is a way to get all nodes that are connected to another node by references. To retrieve for example complete trees or the whole address space, several browse calls are necessary which use the results of previous browse calls. The service allows both the client and the server to restrict the number of the returned results. If the number of results exceeds this maximum, a so-called continuation point is created in the server and passed to the client. The continuation can be passed with the BrowseNext to retrieve the remaining browse results.