Cross Database Queries using IBM Data Studio
For you to execute any SQL statement you have to be connected to some database server; Data Studio does not execute SQL statements. Subsequently, for the three part name (&lt;server&gt;.&lt;schema&gt;.&lt;object&gt;) to work the server you're connected to has to know what the &lt;server&gt; part is.
In the simple case of accessing objects in a database that belongs to the same Db2 for LUW database instance, &lt;server&gt; is the other database name, and no additional setup is required.
However, if the other table is in a database managed by a different instance, or if it belongs to a different DBMS (Db2 for z/OS, Oracle, etc.), you will need to set up a federated data source, whose name you will then use for &lt;server&gt;.