No, by definition you can't have two primary keys on one table (you can have any number of both UNIQUE and NOT NULL constraints, but only one such pair can be called the "primary key constraint"). What you can do though is have one primary key that uses two columns. It's also possible to define sequence objects yourself but I haven't read the DB2 documentation enough to see what control you have over them with regards to things like re/setting their counters. Maybe do something with ON INSERT triggers.
On the other hand, does it really matter? Sorting records with IDs 57,58,59 by ID will put them in the same order as if they had IDs 1,2,3. Try it with your example dataset: [font=monospace]ORDER BY OrdNum,SeqNum[/font] gives you the same result as [font=monospace]ORDER BY id[/font]; SeqNum doesn't contain any information you can't get from the other two columns. You have to expect your sequences to have gaps in them anyway: for your stated purpose they only need to be in the right order - their exact values are irrelevant.
