Exchanging a stored procedure

I have an ESQL/C application that calls various stored procedures, there are also a couple of stored procedures that are called by other stored procedures. Now from time to time it is necessary to update one of these procedures, to fix bugs or to upgrade it. Since it is not possible to lock a stored procedure, what is the best way to handle such exchanges while the application is running? This is a 24/7 application connected to the internet, so there is no time of the day when it stands still. The errors I am getting when I do DROP PROCEDURE, CREATE PROCEDURE and UPDATE STATISTICS FOR PROCEDURE are -721 (procedure no longer valid) and -674 (procedure not found), one in each application process (there are several of them running). I can think of catching these errors and repeating the procedure call, however this might end up in an infinite loop if something goes wrong, so I'd prefer something more robust. --Micha