Access Default Values are assigned as declarative DB2 defaults wherever permissible. But since Access allows more flexibility in specifying Default Values than does DB2, some Default Values are implemented using triggers. Triggers are required, for example, when Default Values perform arithmetic, or built-in functions are employed.
A BEFORE INSERT trigger is created to set explicitly defined defaults when rows are inserted. If the Access field also specifies the “Required” (NOT NULL) attribute, then a BEFORE UPDATE trigger is also created that prevents NULL updates.
If Access Default Values for a corresponding DB2 table containing data are changed, the DB2 table will automatically be rebuilt since ALTER TABLE does not support this type of modification.