1.
SYS用戶具有DBA權(quán)限，并且擁有SYS模式，只能通過(guò)SYSDBA登陸數(shù)據(jù)庫(kù)。是Oracle數(shù)據(jù)庫(kù)中權(quán)限最高的帳號(hào)
SYSTEM具有DBA權(quán)限。但沒(méi)有SYSDBA權(quán)限。平常一般用該帳號(hào)管理數(shù)據(jù)庫(kù)就可以了。
2.
（1）sys -- sysdba
system --sysoper
（2）startup/shutdown/dba管理兩個(gè)都能做
（3）sys擁有數(shù)據(jù)字典(dictionay),或者說(shuō)dictionay屬于sys schema
（4）sysdba比sysoper多了一個(gè)create database的權(quán)限
3.
SYSDBA
Perform STARTUP and SHUTDOWN operations
ALTER DATABASE: open, mount, back up, or change character set
CREATE DATABASE
CREATE SPFILE
ARCHIVELOG and RECOVERY
Includes the RESTRICTED SESSION privilege
Effectively, this system privilege allows a user to connect as user SYS.
SYSOPER
Perform STARTUP and SHUTDOWN operations
CREATE SPFILE
ALTER DATABASE OPEN/MOUNT/BACKUP
ARCHIVELOG and RECOVERY
Includes the RESTRICTED SESSION privilege
This privilege allows a user to perform basic operational tasks, but without the ability to look at user