1. A computer implemented method for managing object to relational one-to-many mapping in a relational database, the method comprising: creating, at a computer, a source clone of a source object in an object model wherein the source object has a primary key value from a source table of the relational database, a relationship clone of a one-to-many relationship in the object model corresponding to the source object, and a target clone of target objects in the object model referenced by the relationship wherein the target objects have foreign key values from target tables of the relational database; retrieving, by the computer, mapping meta-data via a runtime mapping library, wherein the mapping meta-data describes how class attributes of the source object map to columns in the source table, and how the relationship maps to foreign keys in target tables corresponding to the target objects, wherein the foreign keys have the primary key value; determining, by the computer, changes to the source clone and target clone by comparing the source clone with the source object in the object model, and comparing the target clone with the target objects in the object model; and generating, by the computer, a set of database instructions to update changes to the source and target tables in the relational database.