Symptom and confirmed scope
A ClearSCADA 2015 R2 System DSN can authenticate successfully while the Microsoft SQL Server linked-server browser remains empty. In the reported case, the same DSN exposed data to Microsoft Access, and SQL Server connected without an error, but the linked-server tree showed only Catalogs and System Catalogs. Upgrading SQL Express from 2012 R1 to 2014 did not change the behavior.
This evidence separates connectivity from schema browsing: an empty tree does not prove that the ClearSCADA data is inaccessible. The evidence does not establish whether using the System DSN name for both Product Name and Data Source is required, so do not use that configuration detail alone to judge the connection.
Query the ClearSCADA schema directly
Bypass the object browser and address a known ClearSCADA object explicitly. With a linked server named CLEAR, the confirmed query for CDBObject is:
SELECT *
FROM CLEAR..Kernel.CDBObject;The four-part reference leaves the catalog component empty and specifies Kernel as the schema. Replace only the linked-server name or target object when those names are known from the ClearSCADA system.
Troubleshooting and verification procedure
- Confirm that the System DSN works from a client already able to access ClearSCADA data. This validates the DSN credentials and basic connection path.
- Run a known ClearSCADA query rather than relying on the SQL Server object tree. For the documented case, query
CLEAR..Kernel.CDBObject. - If the object names are unknown, inspect the ClearSCADA schema on the ClearSCADA server at
https://localhost/schema/. - Write and test the query inside ClearSCADA, then transfer the verified query structure to SQL Server.
- Confirm success from returned rows or a query result. Do not treat populated linked-server folders as the required verification criterion.
Diagnostic interpretation
| Observation | Supported conclusion | Next action |
|---|---|---|
| The DSN works in Microsoft Access | The reported DSN and ClearSCADA credentials can retrieve data through at least one client | Test a known query from SQL Server |
| SQL Server connects without an error | The linked-server connection is accepted | Do not stop at the empty browser tree |
| Only system catalog folders appear | SQL Server is not browsing the ClearSCADA schema in this case | Use an explicit schema-qualified object reference |
CLEAR..Kernel.CDBObject returns data |
Direct linked-server access works despite the empty tree | Build subsequent queries from verified ClearSCADA schema names |
FAQ
Why is my ClearSCADA linked server empty in SQL Server?
SQL Server may connect successfully without browsing the ClearSCADA schema. Test a known object directly instead of using the linked-server tree as the connection test.
How do I query CDBObject through a ClearSCADA linked server?
For a linked server named CLEAR, run SELECT * FROM CLEAR..Kernel.CDBObject;. A returned result confirms direct access even when no tables appear in the browser.
Where can I find ClearSCADA schema and field names?
On the ClearSCADA server, inspect https://localhost/schema/. Test the intended query inside ClearSCADA before transferring its object and field references to SQL Server.