Oracle Database Foundation

• Oracle Foundation

1. Brief introduction
2. DB instance
3. Table Space
4. Login Identities and Roles
5. User

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Oracle Foundation :

　　Oracle database creation cannot be done with a simple CREATE DATABASE command like SQL Server, although multiple databases can be installed in an Oracle database server, but a database needs to occupy very large memory space.

Therefore, a server typically installs only one database. Each database can have many users, different users have their own database objects (such as database tables), if a user access other users of the database object, must be granted by the other user a certain permission.

Tables created by different users can only be accessed by the current user. As a result, in Oracle development, different applications can only use different user access .

DB instance : 　　

With Oracle official description: An instance is a subset of the computer memory and secondary processing background processes required to access an Oracle database, which is a collection of processes and the memory (SGA) used by those processes.

It is actually a piece of process used to access and use the database, it only exists in memory. Just like the new instance object in Java.

We visit Oracle to access an instance, but if the instance is associated with a database file, it can be accessed, and if not, you will get an error that the instance is not available.

The instance name refers to the name of the database management system that is used in response to a database operation. She is also called SID. The instance name is determined by the parameter instance_name.

table Space :

An Oracle database is a table space for storing physical tables, a database instance can have n table spaces, and a table space can have n tables.

With the database, you can create table spaces.

A tablespace (tablespace) is a logical division of a database, with at least one table space (called the system tablespace) for each database. To facilitate management and improve operational efficiency, you can use additional tablespaces to divide users and applications. For example, the user table space is for general users and the RBS table space is used for rollback segments. A table space can belong to only one database.

To view the table space statements owned by the current user:

SELECT NAME from V$database

CREATE TABLE space Syntax:

Create tablespace tablespace name  datafile          table space data file path  size              table space Initial size autoextend on whether to     expand space automatically

Such as:

Create tablespace db_test  datafile ' D:\oracle\product\10.2.0\userdata\db_test.dbf '  size 50m  Autoextend on;

identities and Roles:

Three connection identities in Oracle Normal and SysDBA and sysyoper

Normal : ordinary user, permission can only query data of some tables

SysDBA: The database administrator, the permissions include: Open the database server, shut down the database server, back up the database, restore the database; Log archive; session limits; Manage functions; Create a database

syssyoper: The database operator, the permissions include: Open the database server, shut down the database server, back up the database, restore the database; Log archive; session limit;

SYS and system are the two accounts installed by default for each Oracle database system. SYS is the owner of all internal database tables, structures, process packages, and so on, and it also has a v$ and data dictionary view and creates all the encapsulated database roles (dba,connect,resource). SYS is the only user who can access a specific internal data dictionary. System is also the user that was created when you installed Oracle for the management of DBA tasks.

When Oracle is created, several users are preset,sys and system and Sott

Account/Password	Identity	Description
Sys/change_on_install	SYSDBA or Sysoper	Cannot log on as NORMAL and can be used as the default system administrator
System/manager	SYSDBA or NORMAL	Cannot log on as Sysoper and can be used as the default system administrator
Scott/tiger	NORMAL	Normal User

Role: Another concept is the database role (role), a database role is a collection of several system permissions.

Oracle user rights to database management or object operations are divided into system permissions and database object permissions. System rights
such as: CREATE session,create TABLE, users with system permissions, allow the corresponding system to
For Database object permissions, such as the increase and deletion of data in the table, users with database object permissions can
To perform the corresponding operation on the owning object.

If you create a new user UserA, but UserA still cannot log on to the system, because he does not have permissions, each user logon system requires at least the role of Create session permissions.

Role name	Introduction description
CONNECT	The main applications are temporary users, especially those who do not need to build a table, and usually only give connect role. CONNECT is a simple permission to use Oracle, A user with the Connect role can establish a connection session with the server (session, client-to-server connection, called a conversation).
RESOURCE	More reliable and formal database users can grant RESOURCE role. RESOURCE Provide additional permissions to the user to create their own tables, sequences, procedures (procedure), triggers (trigger), index, and so on.
Dba	DBA role has all of the system permissions----including unlimited space limits and grants to other users The ability to grant various rights. The user SYSTEM has a DBA role.

User:

Users of Oracle can be created with the Create user command. Its syntax is:

CREATE USER   by password account UNLOCK/Lock (whether locked)

Such as

CREATE USER User  by123456accountUNLOCK

Oracle Database Foundation