SYS A "Magic" USER

SYS is default users, created with the creation of the database. Although sys have much power as it is granted the DBA role but still an ordinary users. Because SYS owns the data dictionary, it is considered a bit more special . 

Anytime, someone connects as SYSDBA, it turns out it's being SYS. That is, if SYSDBA is granted to HR and hr connects as SYSDBA and select user from dual, it reveals he's actually SYS.  SYS is also special  that it is not possible to create a trigger in the sys schema. Also, a logon trigger is not executed when sys connects to the database.

Never ever create objects in the SYS schema.The objects belonging to SYS cannot be exported.We can’t do below database work with any other  user except SYS (SYSDBA).

1.) Database Full Recovery (FULL, UNTIL CANCEL, UNTIL TIME, UNTIL SCN)

2.) Change Database Character Set 

3.) Create Database

4.) Drop Database

5.) Startup and Shutdown
Note : Sysdba privileges cannot be revoked from "sys" user.

Enjoy          J J J