1. Introduction

In Oracle Database, both the SYS and SYSTEM users are administrative accounts, but they have different roles and responsibilities. We’ll briefly discuss these two accounts.

2. SYS Account

• Role: The SYS user is the most powerful account in Oracle, often referred to as the “superuser.”
• Ownership: This account owns all the base tables and views that make up the Oracle data dictionary (the core set of tables that store metadata about the database).
• Access Rights: The SYS account has the highest level of privileges and automatically has the SYSDBA privilege, which allows it to perform tasks like starting up, shutting down, and performing complete system maintenance.
• Data Dictionary: Only the SYS user should directly modify or own data dictionary tables and views because any changes to them can impact the entire database.
• Usage: It is typically used for critical system-level tasks such as database creation, startup, shutdown, backup, and recovery.
• Authentication: The SYS user is authenticated through the Oracle password file or operating system authentication when accessing the database with the SYSDBA privilege.

3. SYSTEM Account

• Role: The SYSTEM account is the default administrative user created during Oracle database installation.
• Ownership: While SYSTEM does not own the core data dictionary tables, it owns important secondary administrative tables and views used for managing the database.
• Access Rights: The SYSTEM user has the DBA role but does not have the SYSDBA privilege by default (though it can be granted). It has broad administrative capabilities but is generally used for less critical administrative tasks compared to the SYS account.
• Usage: It is used for day-to-day administrative tasks, such as managing users, roles, tablespaces, and other database objects. However, it is not involved in managing the core internal structures of the database like SYS.
• Authentication: The SYSTEM account is authenticated using a normal password and can connect as DBA without using SYSDBA.

4. Key Differences

• Privileges: SYS has the highest level of privilege (SYSDBA), while SYSTEM has powerful administrative rights but lacks SYSDBA unless explicitly granted.
• Ownership: SYS owns the core system tables and views (data dictionary), whereas SYSTEM owns administrative objects related to database management.
• Purpose: SYS is used for critical, low-level operations related to the database’s core structure, while SYSTEM handles higher-level administrative tasks like user and role management.

In practice, the SYS account is reserved for system-critical tasks, while the SYSTEM account is more commonly used for routine database administration.