What is the difference between sys and system accounts in Oracle databases? There are two ways to connect to Oracle as a administrator using sqlplus:


sqlplus sys as sysdba
sqlplus system/manager


These accounts should be uses for different purposes, I suppose.

Which tasks are these two schemas meant for? When should I use one or the other among them?
SYS


Automatically created when Oracle database is installed
Automatically granted the DBA role
Has a default password: CHANGE_ON_INSTALL (make sure you change it)
Owns the base tables and views for the database data dictionary
The default schema when you connect as SYSDBA


Tables in the SYS schema are manipulated only by the database. They should never be modified by any user or database administrator, and no one should create any tables in the schema of user SYS. Database users should not connect to the Oracle database using the SYS account.

SYSTEM


Automatically created when Oracle database is installed
Automatically granted the DBA role
Has a default password: MANAGER (make sure you change it)
Used to create additional tables and views that display administrative information
Used to create internal tables and views used by various Oracle database options and tools


Never use the SYSTEM schema to store tables of interest to non-administrative users.

/via