In security guide section 2.1.6. JAAS JDBC Login Module:
https://access.redhat.com/documentation/en-US/Red_Hat_JBoss_A-MQ/6.2/html/Security_Guide/ESBSecureContainer.html#JAASAuth-JDBCLoginModule

Mention the option to configure more than one loginmodule specially in the context of not loosing access to the system if the DB is missconfigured or unreachable.
an example of combining the default configuration with the JDBC one is attached.