D. The last ROLLBACK statement rolls back all DML statements since SAVEPOINT SAVE_4; the last UPDATE was executed before the SAVEPOINT to SAVE_4, therefore the change made by the last UPDATE is unchanged, and the salary remains 1500.
C. The ALTER USER command changes data, even though it resides in the data dictionary; no data in a table can be changed in a READ ONLY transaction.
A, C. You cannot dynamically change the parameter UNDO_MANAGEMENT after the instance has started. You can, however, change the UNDO_TABLESPACE parameter to switch to another undo tablespace while the instance is up and running.
A. Guaranteed undo retention can be set at the tablespace level by using the RETENTION GUARANTEE clause with either ...