Oracle imports constraints and triggers in the end (after row data).
I think the problem is that the data required for referencing (parent table) is being imported after the child table.
I would suggest run first import with rows=n
Second run of import with rows=y and ignore=y to import rows after the table definition and constraints are in place.
I did try with rows=n first, that worked fine. But te second import with rows=y and ignore=y gave me errors ora-02291 integrity constraint violated- parent key not found.
When I tried with constraints=n,
It does the import, but why does it try to enable the constraints at the end even if I put constarints=n.
Is there any option of telling the import not to enable constraints at the end.