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A user can connect with different levels of privileges:

• namely for the database:
  • SYSDBA (the root or administrator of the database)
  • and SYSOPER. SYSOPER allows a user to perform basic operational tasks, but without the ability to look at user data.
• for Automatic Storage Management:
  • SYSASM (the root or administrator of Automatic Storage Management)

Operating system accounts (user) must be members of the OSDBA or OSOPER groups to connect to the database with administrator privileges.

When you connect with a privilege issuing a 'CONNECT / AS SYSDBA' (OR SYSOPER), Oracle checks if your account is a member of the corresponding OS group (for Windows: 'ORA_sid_DBA' or 'ORA_DBA' group).

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