A (not B,not E):The CREATE DATABASE ... ENABLE PLUGGABLE DATABASE SQL statement creates a new CDB. If you do not specify the ENABLE PLUGGABLE DATABASE clause, then the newly created database is a non-CDB and can never contain PDBs.

Explanation/Reference:
Explanation:
The value for TBS_PERCENT_USED specifies the percentage of the tablespace quota when a tablespace is considered full. The value for TBS_PERCENT_FREE specifies the targeted free percentage for the tablespace. When the percentage of the tablespace quota reaches the value of TBS_PERCENT_USED, ADO begins to move data so that percent free of the tablespace quota approaches the value of TBS_PERCENT_FREE. This action by ADO is a best effort and not a guarantee.

Explanation/Reference:
Explanation:
The log files are created only in $ADR_HOME/log
in alert log only alter system is catched.Sun Mar 30 23:30:04 2014ALTER SYSTEM SET enable_ddl_logging=TRUE SCOPE=BOTH;Sun Mar 30 23:32:41 2014ALTER SYSTEM SET enable_ddl_logging=TRUE SCOPE=BOTH;Sun Mar 30 23:39:35 2014ALTER SYSTEM SET enable_ddl_logging=FALSE SCOPE=BOTH;[oracle@ovs trace]$
only in diag/rdbms/.../../log/ two files are capturing this. The xml file is capturing full details and text file having only the commands.
[oracle@ovs log]$ pwd/oraclebase/diag/rdbms/ora12c1/ora12c1/log[oracle@ovs log]$ cat ddl/* create table testing2(a number)
create table testing3( aa number)
[oracle@ovs log]$ cat ddl_ora12c1.logSun Mar 30 23:33:26 2014diag_adl:create table testing2(a number) diag_adl:create table testing3( aa number)
Refernces: http://docs.oracle.com/database/121/REFRN/refrn10302.htm#REFRN10302

The Segment Advisor generates the following types of advice:
*If the Segment Advisor determines that an object has a significant amount of free space, it recommends online segment shrink. If the object is a table that is not eligible for shrinking, as in the case of a table in a tablespace without automatic segment space management, the Segment Advisor recommends online table redefinition(C).
* (D)If the Segment Advisor encounters a table with row chaining above a certain threshold, it records that fact that the table has an excess of chained rows.

The alert log is a chronological log of messages and errors, and includes the
following items:
*All internal errors (ORA-600), block corruption errors (ORA-1578), and deadlock errors
(ORA-60) that occur
*Administrative operations, such as CREATE, ALTER, and DROP statements and
STARTUP, SHUTDOWN, and ARCHIVELOG statements
*Messages and errors relating to the functions of shared server and dispatcher processes
*Errors occurring during the automatic refresh of a materialized view
*The values of all initialization parameters that had nondefault values at the time the
database and instance start
Note:
*The alert log file (also referred to as the ALERT.LOG) is a chronological log of messages
and errors written out by an Oracle Database. Typical messages found in this file is:
database startup, shutdown, log switches, space errors, etc. This file should constantly be
monitored to detect unexpected messages and corruptions.