If you have a lot of LOB data to move around with Oracle import/export utilities this might help you out. The default for the COMMIT parameter is No.
COMMIT=N : For tables that have a LOB column, commit is performed after loading each table
This is much faster but be aware that you will use more Rollback space since each table will be committed in one large transaction.
COMMIT=Y : For tables that have a LOB column, commit is performed after each row (slow!, much overhead added because so many transactions are used to import the data)