Explanation/Reference:
Explanation:
AB: You can make individual table columns invisible. Any generic access of a table does not show the invisible columns in the table. For example, the following operations do not display invisible columns in the output:
* SELECT * FROM statements in SQL
* DESCRIBE commands in SQL*Plus
* %ROWTYPE attribute declarations in PL/SQL
* Describes in Oracle Call Interface (OCI)
Incorrect Answers:
D: You can make invisible columns visible.
You can make a column invisible during table creation or when you add a column to a table, and you can later alter the table to make the same column visible.

"Oracle Grid Infrastructure for a standalone server includes Oracle Restart and Oracle Automatic Storage Management. Oracle combined the two infrastructure products into a single set of binaries that is installed into an Oracle Restart home." References: http://docs.oracle.com/cd/E16655_01/install.121/e17735/oraclerestart.htm#NTDBI999

Explanation/Reference:
Explanation:
If you run multiple AUDIT statements on the same unified audit policy but specify different EXCEPT users, then Oracle Database uses the last exception user list, not any of the users from the preceding lists. This means the effect of the earlier AUDIT POLICY ... EXCEPT statements are overridden by the latest AUDIT POLICY ... EXCEPT statement.
Note:
* The ORA_DATABASE_PARAMETER policy audits commonly used Oracle Database parameter settings.
By default, this policy is not enabled.
* You can use the keyword ALL to audit all actions. The following example shows how to audit all actions on the HR.EMPLOYEES table, except actions by user pmulligan.
Example Auditing All Actions on a Table
CREATE AUDIT POLICY all_actions_on_hr_emp_pol
ACTIONS ALL ON HR.EMPLOYEES;
AUDIT POLICY all_actions_on_hr_emp_pol EXCEPT pmulligan;

E: By default, flashback archiving is disabled for any table. You can enable flashback archiving for a table if you have the FLASHBACK ARCHIVE object privilege on the Flashback Data Archive that you want to use for that table.
D: Creating a Flashback Data Archive
/ Create a Flashback Data Archive with the CREATE FLASHBACK ARCHIVE statement, specifying the following:
Name of the Flashback Data Archive
Name of the first tablespace of the Flashback Data Archive
(Optional) Maximum amount of space that the Flashback Data Archive can use in the first tablespace
/ Create a Flashback Data Archive named fla2 that uses tablespace tbs2, whose data will be retained for two years:
CREATE FLASHBACK ARCHIVE fla2 TABLESPACE tbs2 RETENTION 2 YEAR;

* A PDB would have its SYSTEM, SYSAUX, TEMP tablespaces.It can also contains other user created tablespaces in it. *
*Oracle Database creates both the SYSTEM and SYSAUX tablespaces as part of every database.
*tablespace_datafile_clauses
Use these clauses to specify attributes for all data files comprising the SYSTEM and SYSAUX
tablespaces in the seed PDB.
Incorrect:
Not D: a PDB can not have an undo tablespace. Instead, it uses the undo tablespace belonging to
the CDB.
Note:
* Example: CONN pdb_admin@pdb1
SELECT tablespace_name FROM dba_tablespaces;
TABLESPACE_NAME SYSTEM SYSAUX TEMP USERS
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