We are planning to migrate Toplink version 9.0.3 to eclipselink. We have recently migrated our Database to 11i. I saw below useful link and came to know not major hurdles with migration. Is there any major issues/lot of coding changes with respect to DAO logic or is is just updating Model classes and ORM mappings?
You should be able to run the EclipseLink package-renamer to migrate from TopLink to EclipseLink. This should be fairly straight forward. There may be some minor issues if you were using deprecated API or some changes in behavior.
You may choose to migrate to JPA at the same time. This would be more involved, but may not be too difficult if your data access is encapsulated in a DAO layer.