Database administrator < three >

Database administrator

? Introduced

Each Oracle database should have at least one database administrator (DBA), and one DBA is sufficient for a small database, but for a large database

Multiple DBAs may be required to share different management responsibilities. So what is the main job of a database administrator:

? Duty

1. Installing and upgrading the Oracle database

2. Build library, table space, table, view, index "

3. Develop and implement backup and recovery plans

4. Database Rights Management, tuning, troubleshooting

5. For advanced DBAs, who are required to participate in project development, write SQL statements, stored procedures, triggers, rules, constraints, packages

The Oracle installation automatically generates SYS users and system users:

(1) SYS user is superuser, has the highest privilege, the user's default password is Change_on_install

(2) The system user is the management operator, the permissions are also very large, the default password is the manager

? The user who manages the database is primarily SYS and system

(Sys seems to be the chairman, the system seems to be the general manager, the chairman is larger than the general manager, but usually the general manager)

In the previous we have mentioned these two users, the difference is mainly:

1. The most important difference is that the data stored is of different importance

SYS: the base tables and views of all Oracle data dictionaries are stored in the SYS user, and these base tables and views are critical to the operation of Oracle by the database

Self-maintenance, no user can change it manually. SYS user has dba,sysdba,sysoper roles or permissions and is the highest user with Oracle permissions.

System: Used to hold sub-level internal data, such as some of Oracle's features or tools for managing information. System users have DBA,SYSDBA roles or systems rights

Limit.

Look at the picture:

SYSDBA can build database, Sysope can't build database

2. The second difference, the different permissions.

SYS user must be logged in as SYSDBA or as Sysoper. Unable to log in to the database in normal mode

If the system is logged in normally, it is actually a normal DBA user, but if you log in as SYSDBA, the result is actually logged in as a sys user,

We can see that from the login information.

SYSDBA and Sysoper permission difference diagram, see figure:

Sysdba>sysoper>dba

Can see: As long as the Sysoper have permissions, sysdba have; Blue is where they differ. (The biggest difference is: SYSDBA can create a database,

Sysoper cannot create a database)

? User with DBA Authority

A DBA user is a database user with a DBA role. Privileged users can perform special operations such as launching instances, shutting down instances, and DBA users only when starting the database

To perform various administrative tasks.

(equivalent to saying that DBAs don't have both the startup and shutdown permissions)

Two major users, three important permissions, their differences and connections, we have to figure out

Managing Initialization parameters

? Manage initialization parameters (an important knowledge point of tuning, what makes it possible to tune a database?) is because it can modify some parameters of the database to fix

Is

Initialization parameters are used to set the characteristics of an instance or database. Oracle9i provides more than 200 initialization parameters, and each initialization parameter has a default value.

? Display initialization parameters

(1) Show parameter command

? How to modify Parameters

If you want to modify these initialization parameters, you can go to the file D:\oracle\admin\myoral\pfile\init.ora file to modify, for example, to repair

Change the name of the instance

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