Problem:

Need information on calling stored procedures that return data.

Resolution:

If nothing is specified in the call statement then INPUT is assumed.

You can specify OUT or INOUT (for both input and output)

ex. EXEC SQL CALL MFTEST (:host1 INOUT, :host2 out, :host3 ) END-EXEC

Look in Bookshelf>Database Access> chapter 11 Stored Procedures.