Which three actions are performed by Database Upgrade Assistant (DBUA)? (Choose three.)
A.It recompiles all stored PL/SQL code by using utlrp.sql. B.It empties the RECYCLE BIN. C.It performs prerequisite checks to verify if the Oracle database is ready for upgrade. D.It sets all user tablespaces to “read-only” before starting the upgrade. E.It removes the AUDSYS schema and the AUDIT_ADMIN and AUDIT_VIEWER roles F.It increases tablespace size, if required, to meet upgrade requirements.正确答案ACD
