Dear Sandeep Rajanala,
In general the existing ABAP code(reports, classes, module pool programs, function modules etc) runs on SAP HANA as before and the existing dictionary objects like tables, views, DDIC types and structures continues to exist and work as before after migration.
However if the existing ABAP Code relies on the technical specifics of the old database , ABAP Code changes might be necessary(which is the case for any database migration ).
For example,
- Your ABAP code uses a feature that is specific to the old database and not in the SQL standard and therefore not in Open SQL(consumed via Native SQL using EXEC SQL or ADBC interface)
- You have ABAP code that relies on unspecified undocumented implementation behaviour of the old database
the above cases may need minor code changes in ABAP during HANA migration inorder to ensure that your ABAP Code runs with functional correctness after migration.
The SAP note 1785057 gives guidelines on migrating the existing ABAP Custom Code for HANA.
Additionally we have several code inspector checks to find the ABAP code that requires changes and you can find details about these check in SAP note 1912445.
In addition you can find an elaborate guide for transitioning custom ABAP code to HANA here which has a dedicated section on required and recommended adaptations during custom code migration.
You can also find the recording of the SAP Teched 2013 hands on session which focuses completely on ABAP Custom Code migration aspects for HANA here
Hope this answers your question and gives you some pointers on how you could prepare your ABAP for migrating to HANA.
Please revert back if you have further questions.
Best Regards
Sundar.