Explanation
http://docs.oracle.com/database/121/ADMIN/cdb_pdb_admin.htm#ADMIN14017

Explanation/Reference:
Explanation:
Note:
Providing a UNIX Group Name
If you are installing a product on a UNIX system, the Installer will also prompt you to provide the name of the group which should own the base directory.
You must choose a UNIX group name which will have permissions to update, install, and deinstall Oracle software. Members of this group must have write permissions to the base directory chosen.
Only users who belong to this group are able to install or deinstall software on this machine.

*Automatic segment space management (ASSM) is a simpler and more efficient way of managing space within a segment. It completely eliminates any need to specify and tune the pctused,freelists, and freelist groups storage parameters for schema objects created in the tablespace. If any of these attributes are specified, they are ignored. *Oracle introduced Automatic Segment Storage Management (ASSM) as a replacement for traditional freelists management which used one-way linked-lists to manage free blocks with tables and indexes. ASSM is commonly called "bitmap freelists" because that is how Oracle implement the internal data structures for free block management.
Note:
* Buffer busy waits are most commonly associated with segment header contention onside
the data buffer pool (db_cache_size, etc.).
*The most common remedies for high buffer busy waits include database writer (DBWR)
contention tuning, adding freelists (or ASSM), and adding missing indexes.

Explanation/Reference:
Explanation:
* You can create a password file using the password file creation utility, ORAPWD.
* Adding Users to a Password File
When you grant SYSDBA or SYSOPER privileges to a user, that user's name and privilege information are added to the password file. If the server does not have an EXCLUSIVE password file (that is, if the initialization parameter REMOTE_LOGIN_PASSWORDFILE is NONE or SHARED, or the password file is missing), Oracle Database issues an error if you attempt to grant these privileges.
A user's name remains in the password file only as long as that user has at least one of these two privileges. If you revoke both of these privileges, Oracle Database removes the user from the password file.
* The syntax of the ORAPWD command is as follows:
ORAPWD FILE=filename [ENTRIES=numusers]
[FORCE={Y|N}] [IGNORECASE={Y|N}] [NOSYSDBA={Y|N}]
* IGNORECASE
If this argument is set to y, passwords are case-insensitive. That is, case is ignored when comparing the password that the user supplies during login with the password in the password file.

*You can include the CONTAINER clause in several SQL statements, such as the CREATE USER, ALTER USER, CREATE ROLE, GRANT, REVOKE, and ALTER SYSTEM statements. * * CREATE ROLE with CONTAINER (optional) clause /CONTAINER = ALL Creates a common role. / CONTAINER = CURRENT Creates a local role in the current PDB.