How to delete a procedure which name is ambigous?
This happens when you have 2 or more procedures, with the same name, but with different numbers of input parameters.

For example, you have created 2 procedures:

CREATE PROCEDURE myProc(param1)
...
CREATE PROCEDURE myProc(param1, param2)
...


To delete the second one, you have 2 options:

The easy one: 

DROP PROCEDURE myProc(param1, param2);


The hard one:

dbaccess DB -
select procname, procid, numargs from sysprocedures where procname like 'myProc';
procname  myProc
procid    1
numargs   1

procname  myProc
procid    2
**numargs   2**

UPDATE sysprocedures SET procname='myProcOLD' WHERE procid=2;
DROP PROCEDURE myProcOLD;


Even if the first method is dead simple, the first time I got called in the middle of the night for this same problem, I've chosen the second. My bad ...