@yashpande
More and more time is passing since I've used ECM and I start to forget things but...
Shouldn't you add custom fields via UDF tables?
CASE_UDF_DEF
CASE_UDF_<CHAR|NUM>_VALUE
ECM uses an Entity-Attribute-Value model and additional columns and even tables should get defined via data and not via structural changes (changes to DDL).
The UDF_DEF tables get used to define virtual tables and columns, the _UDF_<CHAR|NUM|...>_VALUE tables get used to store such user defined columns (for existing or newly defined tables).
I'd be very cautious with DDL changes and should that be possible without breaking ECM then you'd certainly would still have to define the column in some _DEF table and also add it to the _VERSION table.
Below the steps required to customize ECM (found in some in-between outdated training material but should still be valid):
- Customizing Data Model
- Customizing UI Definitions
- Customizing Page Elements
- Customizing Valid Values
- Customizing Application Behavior