Differences between system and SYS in Oracle databases

http://www.cnblogs.com/phoebus0501/archive/2011/01/17/1937141.html SYS: With DBA, SYSDBA, Sysoper (System Operator) roles or permissions,
is the highest user of Oracle permissions and can only log on as SYSDBA or Sysoper and cannot log in as normal.
System: With DBA, SYSDBA permissions, or roles, you can log on as a normal user. • "Sysdba, Sysoper, dba difference" SYSDBA User: Can change character set, create delete database, after login user is sys (shutdown, startup) Sysoper: User cannot change character set, can't create, delete database,
After landing, the user is public (shutdown, startup) DBA User: A variety of administrative work can be performed only after the database is started. sysdba> sysoper> Common DBA 1)    The most important difference is the importance of storing data in different "SYS" All Oracle data dictionaries have base tables and views that are stored in the SYS user,
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.



The SYS user has roles or permissions such as Dba,sysdba,sysoper and is the highest user of Oracle permissions. The "system" user holds the secondary level of internal data, such as some Oracle features or management information for the tool.



The system user has the normal DBA role permissions.

2    The second difference, the different permissions.

"System" users can only log on em as normal, unless you grant SYSDBA system privileges or syspoer system privileges.

　"SYS" User has "SYSDBA" or "sysoper" system privileges, login em can only use these two identities, can not use normal.

　　Login to Oracle with the SYS user, execute SELECT * from V_$pwfile_users, and query to users with SYSDBA permissions, such as: sql> select * from V_$pwfile_users; USERNAME SYSDBA sysoper SYS true    SYSDBA and sysoper What are the differences between normal, SYSDBA, and Sysoper?

Normal is the other two users, you look at the permissions they have to know the SYSDBA has the highest system permissions, after logging is the SYS sysoper mainly used to start, close the database, sysoper after the user is public sysdba and Sysope R belongs to system privilege, also known as administrative privilege, with some administrative-level permissions such as database open shutdown SYSDBA and sysoper specific permissions can be seen in the following table: System if log on normally, it It's an ordinary DBA user, but if you log in as SYSDBA, the result is actually logged in as a SYS user, which is similar to the sudo feeling in Linux, as we can see from the login information. So when you connect to the database as SYSDBA, the objects you create are actually generated in the Sys.

Other users are the same, if as SYSDBA login, but also as a SYS user login, see the following experiment: sql> create user strong identified by strong;

User has created.

Sql> Conn [Email=strong/strong@magick]strong/strong@magick[/email] as SYSDBA;

is connected.

Sql> Show user;

USER is "SYS" sql> create TABLE Test (a int);

Table has been created.

Sql> Select owner from dba_tables where table_name= ' test ';

Row not selected because Oracle automatically capitalizes when the table is created, it does not exist in lowercase; sql> select owner from dba_tables where Table_name= ' TEST '; OWNER------------------------------SYS Ø         Differences between DBAs and SYSDBA what's the difference between a DBA and a sysdba? Before I explain this, I need to say something about the creation of Oracle services • Create an instance → a startup instance → Create a database (sYstem table space is required) startup process • Instance startup → load database → Open database sysdba, is to manage the Oracle instance, its existence does not depend on the entire database to start completely, as long as the instance starts, he already exists, log in as the SYSDBA identity, mount the database, Open the database. 
   Only the database is open, or when the entire database is fully booted, the DBA role has a basis for existence.