Xi. Oracle Database Administrator

First, the database administrator
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 it may require multiple DBAs to share different management responsibilities. So what is the main job of a database administrator:
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

Second, the user of the management database is the SYS and system (SYS seems to be the chairman, the system seems to be the general manager, the chairman is bigger than the general manager, but usually the total
Manager Officer)
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 and are maintained by the database itself and cannot be changed manually by any user. 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. The system user has DBA,SYSDBA roles or systems permissions.
Note: SYSDBA can build a database, Sysoper cannot build a database

2. The second difference, the different permissions.
SYS user must be logged in as SYSDBA or as Sysoper. You cannot log on to the database as normal.
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, as we can see 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 not 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 an instance, shutting down an instance, and a DBA user may perform various administrative tasks only after the database is started. (It's equivalent to saying that DBAs don't have both the startup and shutdown permissions).
Two major users, three important permissions, their differences and connections, everyone to figure out.

three, manage initialization parameters
1), Manage initialization parameters (an important point of tuning, what can I do to tune a database?). Because it can modify some parameters of the database.
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.
2), display initialization parameters: Show parameter
3), how to modify the parameters
It should be noted that if you want to modify these initialization parameters, you can go to the file D:\oracle\admin\myoral\pfile\ Init.ora the file to be modified.