title: jpa can't execute a simple query
body: <p>I have to retrieve data from a table in db2 using jpa <br>
  after all configuration and mapping <br>
  when I try to execute a query using the entity manager I get errors don't know where is the problem exactly.
   the message error :<code>Error 500: &lt;openjpa-2.1.1-SNAPSHOT-r422266:1141200 fatal general error&gt; org.apache.openjpa.persistence.PersistenceException: DB2 SQL Error: SQLCODE=-204, SQLSTATE=42704, SQLERRMC=DB2ADMIN.CATEGORIE, DRIVER=4.8.86 {prepstmnt 85179437 SELECT t0.CODE_CAT, t0.LIBELLE_CAT FROM CATEGORIE t0 } [code=-204, state=42704]SQLCA OUTPUT[Errp=SQLNQ1FC, Errd=-2145779603, 0, 0, 0, -10, 0] DB2 SQL Error: SQLCODE=-204, SQLSTATE=42704, SQLERRMC=DB2ADMIN.CATEGORIE, DRIVER=4.8.86 DB2 SQL Error: SQLCODE=-727, SQLSTATE=56098, SQLERRMC=2;-204;42704;DB2ADMIN.CATEGORIE, DRIVER=4.8.86 DB2 SQL Error: SQLCODE=-727, SQLSTATE=56098, SQLERRMC=2;-204;42704;DB2ADMIN.CATEGORIE, DRIVER=4.8.86 FailedObject: select c from Categorie c [java.lang.String]</code></p>