You have a production instance running on your server. UNDO_RETENTION is not long enough to
satisfy read-consistency requirements. How do you change the UNDO_RETENTION value?
A.
by executing the ALTER SYSTEM .. command
B.
by re-creating the control file with a new value for UNDO_RETENTION
C.
by executing the ALTER DATABASE.. command in the MOUNT state
D.
by executing UPDATE.. statement on V$PARAMETER to change the value of UNDO_RETENTION
To set the minimum undo retention period:
Do one of the following:
Set UNDO_RETENTION in the initialization parameter file.
UNDO_RETENTION = 1800
Change UNDO_RETENTION at any time using the ALTER SYSTEM statement:
ALTER SYSTEM SET UNDO_RETENTION = 2400;
The effect of an UNDO_RETENTION parameter change is immediate, but it can only be honored if the current undo tablespace has enough space.