Official limits for `ServerCapabilities` for the `Server Profiles`|OPC Certification and Interoperability Testing|Forum|OPC Foundation

Hello Alexej,

this depends on the specification version you are looking at. But in general you'll find this information by looking at the Profile Embedded 2017 UA Server Profile (opcfoundation.org) in the profile application. When you check the included profiles, facets and conformance units, you find the following information:

• Support minimum 2 parallel Sessions (total for all Clients).
• Support minimum 1 continuation point per Session.
• Support at least 2 Subscriptions per Session. This number has to be supported for at least half of the minimum required sessions.
• Support at least 5 Publish Service requests per Session. This number has to be supported for at least half of the minimum required sessions. Support, as a minimum, the number of Publish requests per session as the size of the NotificationMessage retransmission queue for Republish.
• Support at least 100 MonitoredItems per Subscription.
  This number has to be supported for at least half of the required Subscriptions for half of the required Sessions.
• Support at least 2 queue entries for MonitoredItems.
  Servers often will adapt the queue size to the number of currently MonitoredItems. However, it is expected that Servers support this minimum queue size for at least one third of the supported MonitoredItems.

Please check the Profile Application for more details and requirements for this profile. I hope this helps. 

Regards,
Alexander Allmendinger