Will updating a large amount of data in Oracle cause the undo space to explode

Need to update recently Oracle A lot of historical data in ( about 5 Billion bars ), You need to put one in each int Change the field , Would you like to know if you will undo Space blasting , Or is there any other risk .

Try... In a test environment update Now , And found that DBA_DATA_FILE Inside BYTES No change in size , What is the reason , This field is not undo The size of