data type "serial"

So how do you store something in data type serial?
I've created the column but everytime I attempt to do an update I get
back the error message that I can't store a duplicate key.

table_col_seq.last_value = 1
increment = 1
maxvalue = 2billion something

I've tried storing 1,2,some other number in "serial" in the main
table to no avail. What is the magic to get this to work. There
appears to be no documentation anywhere on the necessary SQL commands
to cycle the generator. I've tried the method used for Oracle SQL but
that does not work. I'm a bit of a newbie at this.

Michael
Michael@bizsystems.com