Can we alter the embedded database of openfire ?

Actully i want to modify the OFUSER table's column "Name" in the database. i want to make it unique and not null. i try to alter it using dbaccess plugin and run this query

ALTER TABLE OFUSER MODIFY name varchar(100) not null;

but this gives me error:

class org.jivesoftware.openfire.plugin.dbaccess.db_002daccess_jsp: SQL Error: java.sql.SQLException: Unexpected token: MODIFY in statement [ALTER TABLE OFUSER MODIFY]

so my question is, is it possible to do so?