1. SYS用户具有DBA权限，并且拥有SYS模式，只能通过SYSDBA登陆数据库。是Oracle数据库中权限最高的帐号 SYSTEM具有DBA权限。但没有SYSDBA权限。平常一般用该帐号管理数据库就可以了。 2. （1）sys -- sysdba system --sysoper （2）startup/shutdown/dba管理两个都能做 （3）sys拥有数据字典(dictionay),或者说dictionay属于sys schema （4）sysdba比sysoper多了一个create database的权限 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 data