Oracle Data Pump disable redo logging when loading data into tables and when creating indexes.
The new TRANSFORM option introduced in data pumps import provides the flexibility to turn off the redo generation for the objects during the course of import. The Master Table is used to track the detailed progress information of a Data Pump job.
The Master Table is created in the schema of the current user running the Pump Dump export or import, and it keeps tracks of lots of detailed information.