Martin,
Not an alias as in aliased table/view reference, but an alias as in created alias. See here: https://www.ibm.com/support/knowledgecenter/SSEPEK_10.0.0/sqlref/src/tpc/db2z_aliasandsynonym.html
In that screenshot, ADJEXCL is the alias.
I am using Toad Data Point 4.0.0.613 and DB2 for z/OS 10. By the way, this works perfectly in DbVisualizer with the same alias, same database, same server, so I doubt it’s either a syntax or permissions issue.
Thank you.