Explanation
* Creating a PDB
Rather than constructing the data dictionary tables that define an empty PDB from scratch, and then populating its Obj$ and Dependency$ tables, the empty PDB is created when the CDB is created. (Here, we use empty to mean containing no customer-created artifacts.) It is referred to as the seed PDB and has the name PDB$Seed.
Every CDB non-negotiably contains a seed PDB; it is non-negotiably always open in read-only mode. This has no conceptual significance; rather, it is just an optimization device. The create PDB operation is implemented as a special case of the clone PDB operation. The size of the seed PDB is only about 1 gigabyte and it takes only a few seconds on a typical machine to copy it.

Note:
*An incremental level 0 backup backs up all blocks that have ever been in use in this database.
*In a cumulative level 1 backup, RMAN backs up all the blocks used since the most recent level 0 incremental backup.
*Oracle Block Change Tracking Once enabled; this new 10g feature records the modified since last backup and stores the log of it
in a block change tracking file using the CTW (Change Tracking Writer) process. During backups RMAN uses the log file to identify the specific blocks that must be backed up. This improves RMAN's performance as it does not have to scan whole datafiles to detect changed blocks. Logging of changed blocks is performed by the CTRW process which is also responsible for writing data to the block change tracking file.

D: The database internally uses standard file system interfaces to create and delete files as needed for the following database structures:
Tablespaces Redo log files Control files Archived logs Block change tracking files Flashback logs RMAN backups
Note:
* Using Oracle-managed files simplifies the administration of an Oracle Database. Oracle-managed files eliminate the need for you, the DBA, to directly manage the operating system files that make up an Oracle Database. With Oracle-managed files, you specify file system directories in which the database automatically creates, names, and manages files at the database object level. For example, you need only specify that you want to create a tablespace; you do not need to specify the name and path of the tablespace's datafile with the DATAFILE clause.
http://www.oracle-base.com/articles/9i/oracle-managed-files.php http://docs.oracle.com/cd/B10500_01/server.920/a96521/omf.htm Reference: What Are Oracle-Managed Files?

Explanation/Reference:
Explanation:
* orapwd
/You can create a database password file using the password file creation utility, ORAPWD.
The syntax of the ORAPWD command is as follows:
orapwd FILE=filename [ENTRIES=numusers] [FORCE={y|n}] [ASM={y|n}]
[DBUNIQUENAME=dbname] [FORMAT={12|legacy}] [SYSBACKUP={y|n}] [SYSDG={y|n}]
[SYSKM={y|n}] [DELETE={y|n}] [INPUT_FILE=input-fname]
force - whether to overwrite existing file (optional),
* v$PWFILE_users
/12c: V$PWFILE_USERS lists all users in the password file, and indicates whether the user has been granted the SYSDBA, SYSOPER, SYSASM, SYSBACKUP, SYSDG, and SYSKM privileges.
/10c: sts users who have been granted SYSDBA and SYSOPER privileges as derived from the password file.
ColumnDatatypeDescription
USERNAMEVARCHAR2(30)The name of the user that is contained in the password file SYSDBAVARCHAR2(5)If TRUE, the user can connect with SYSDBA privileges
SYSOPERVARCHAR2(5)If TRUE, the user can connect with SYSOPER privileges Incorrect Answers:
E: The format of the v$PWFILE_users file is already in 12c format.