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?
EclipseLink supports the majority of the TopLink 9.0.3 API, it just has different package names. So for most things the migration should be just a matter of running the package renamer on your code.
Some deprecated methods have been removed in EclipseLink, so if you are using these you may need to switch to their replacements.
TopLink 9.0.3 is quite old, so there may be some changes that affect your code depending on how complex it is.
EclipseLink supports the native API, but you could also take the opportunity to migrate to JPA. This would be more involved, but put you on the latest standard. It should not be too difficult if you have your persistence encapsulated in a DAO layer.