Does Migrating from one database to another database requires comprehensive change in the Entity Beans? I have oracle 11g express edition and I want to move to MS Sql?
No.Your entity class can remain the same. However, you may have to change the primary key generation strategy. You may also have to change values of some attributes of the @Column annotation.
Your tables may slightly change due to the fact that different databases have their own ways of storing data. You can regenerate the tables by editing your persistence.xml
<properties>
<property name="javax.persistence.schema-generation.database.action" value="drop-and-create"/>
</properties>