Overview of Operating System Authentication Enabled at Installation

When you install Oracle Database, a special Windows local group called ORA_DBA is created (if it does not already exist from an earlier Oracle Database installation) and the Oracle Installation User is automatically added to it.

Members of local group ORA_DBA automatically receive the SYSDBA privilege. The ORA_DBA group is also created for each Oracle home called ORA_HOMENAME_DBA group. This group is automatically populated with the Oracle Home User for the Oracle home.

Note:

If you use a domain account for database administration, then that domain account must be granted local administrative privileges and ORA_DBA membership explicitly. It is not sufficient for the domain account to inherit these memberships from another group. You must ensure that the user performing the installation is in the same domain as this domain account. If not, it results in an NTS authentication failure.

Membership in ORA_DBA enables you to:

Connect to local Oracle Database servers without a password with the command
```
SQL> CONNECT / AS SYSDBA
```
Connect to remote Oracle Database servers without a password with the command
```
SQL> CONNECT /@net_service_name AS SYSDBA 
```
where net_service_name is the net service name of the remote Oracle Database server
Perform database administration procedures such as starting and shutting down local databases
Add additional Windows users to ORA_DBA, enabling them to have the SYSDBA privilege

Parent topic: Authenticating Database Users with Windows