the error "identifier too long" is probably because a column name is longer than 30 characters, which is the Oracle size limit on object names.
review the table you are trying to migrate and see if that is it.
it could also be data related, where you are sticking a varchar(30) into a VARCHAR2(20) column, or something.
help us help you! If you post a question, make sure you include a CREATE TABLE... statement and INSERT INTO... statement into that table to give the volunteers here representative data. with your description of the problem, we can provide a tested, verifiable solution to your question! asking the question the right way gets you a tested answer the fastest way possible!