Hi @Yongsu Lee,

I think what's worth checking first is whether OUTRUN_DEV itself even has visibility into the external database not just whether the function specifically is blocked.

Try logging into SQL Server Management Studio using the OUTRUN_DEV login itself. Once connected as OUTRUN_DEV, run something simple like:

SELECT * FROM textdb.dbo.SomeTable;

• If nothing comes back / access denied → OUTRUN_DEV doesn't have basic access to textdb at all yet. That's the first thing to fix the user needs to exist inside textdb (mapped to that login) before any grant on a specific function will matter.
• If data comes back fine → OUTRUN_DEV does have general access to textdb, which narrows it down: the problem is specific to FN_FUNCTION itself. In that case, double check the EXECUTE grant was issued inside textdb's own context (not while connected to outsystems_DEV), and that it's pointing at the correct schema and function name.

So in short: confirm OUTRUN_DEV can see textdb at all first, logged in as that exact login then, if that checks out, you can dig into permissions on that one function specifically.

If possible, you might be able to skip most of this instead of granting broad table/database access, you can scope permissions down to just FN_FUNCTION itself and consuming it using Integration studio, nothing else in textdb.

@Yongsu Lee : As far as I understand, the EXECUTE permission needs to be granted to the user configured for the external database connection in Service Center ->  Administration ->  Database Connections.  In the screenshot, the database connection is using the user demouser, so the EXECUTE permission should be granted to demouser, not OUTRUN_DEV. 

A detailed instruction on how to setup is given at https://www.outsystems.com/forums/discussion/14867/how-to-execute-stored-procedures/