Thanks but this does not seem right for the case I am facing.
The procedure declaration is missing 'inTabA' and 'outTabA', where 'inTabA' contains the data to be processed and 'outTabA' the results.
Hence, the procedure declaration for procedure A would have to be:
CREATE PROCEDURE proc_a (IN inTabA tt_TabA, OUT outTabA tt_TabA)
LANGUAGE SQLSCRIPT READS SQL DATA
AS...
and for B it would be:
CREATE PROCEDURE proc_b (IN inTabB tt_TabB, OUT outTabB tt_TabB)
LANGUAGE SQLSCRIPT READS SQL DATA
AS...
Where the types tt_TabA and tt_TabB are specified via CDS I think it is called.
What I am (still) assuming/fearing is that a loop-construct is needed over 'inTabA'. Am I wrong (I hope so 
)???