Is not allowed to use "0" in an INTEGER filed that is part of a primary key?

Hi all,

I'm using OJB 1.0.3.
I defined a primary key in respository descriptor consisting of three
fields.
Two fields are "VARCHAR", one is "INTEGER".

When I try to insert multiple objects with identical values in the
VARCHAR fields and a value of "0" in the INTEGER field, then multiple
records are inserted into database.
Using a value > 0 for the INTEGER field inserts only one record, which
is correct (other records are rejected).

So it seems to me that is not allowed to use "0" in an INTEGER filed
that is part of a primary key. Am I right?

Thanks................Frank