Hi... Thanks for the quick response! My primary key is a serializable java object. (Doesn't seem to be many examples/people which use this approach). It always works when I use the hypersonic db. The primary key object get stored as a blob. It also used to work when I used MySQL with CMP1. Are there any problems with having 'custom' objects as your primary key class when using MySQL etc? It I convert the primary to use an Integer for example everything works fine.
I have included an extract of my ejb-jar file below. Maybe it will help...


<ejb-name>Title</ejb-name>
<local-home>za.co.connectivit.ptisan.misc.TitleLocalHome</local-home>
za.co.connectivit.ptisan.misc.TitleLocal
<ejb-class>za.co.connectivit.ptisan.misc.TitleBean</ejb-class>
<persistence-type>Container</persistence-type>
<prim-key-class>za.co.connectivit.ptisan.misc.TitleID</prim-key-class>
False
<cmp-version>2.x</cmp-version>
<abstract-schema-name>TitleBean</abstract-schema-name>
<cmp-field>
<field-name>titleID</field-name>
</cmp-field>
<cmp-field>
<field-name>name</field-name>
</cmp-field>
<cmp-field>
<field-name>description</field-name>
</cmp-field>
<primkey-field>titleID</primkey-field>
<resource-ref>
<res-ref-name>jdbc/mySQLDS</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>

By the look of things MySQL does allow a primary key data type to be larger 255. After careful consideration I have decided to change my approach with regard to using 'custom' java objects as primary keys. I am going to go the unique OID route. I don't want to have to limit my choice in databases because to primary key/indexing restrictions.

Thanks for all the help.