OS_AUTHENT_PREFIX External Authentication in Oracle Database 19c

Let’s make an extenal authentification example, so the operating system authentication (OS authentication) allows users to connect to Oracle without providing a database password. Instead, Oracle trusts the operating system user account.

In this article, we will explain:

• What OS_AUTHENT_PREFIX is
• How to configure an externally authenticated user
• Example on Oracle 19c (Oracle Linux)

1. What is OS_AUTHENT_PREFIX?

The parameter OS_AUTHENT_PREFIX defines the prefix Oracle adds to operating system usernames when mapping them to database users.

Let’s check the current value:

SQL> show parameter os_authent_prefixNAME                 TYPE     VALUE
-------------------- -------- ----------------
os_authent_prefix    string   ops$

This means:

If the OS user is:

wadhah

Oracle expects the database username to be:

ops$wadhah

(Default behavior in many installations is OPS$.)

2. Creating an Externally Authenticated User

Now we create the database user that matches the OS user.

SQL> CREATE USER OPS$wadhah IDENTIFIED EXTERNALLY;
User created.
SQL> grant connect to OPS$wadhah;
Grant succeeded.

3. What does IDENTIFIED EXTERNALLY mean?

It means:

• No database password is stored
• Authentication is delegated to the operating system
• Oracle trusts the OS login

4. Creating the Operating System User (Linux)

Switch to root and create the OS user:

[root@admin19c ~]# useradd wadhah

Now switch to that user:

[root@admin19c ~]# su - wadhah

Set the Oracle environment:

[wadhah@admin19c ~]$ . oraenv
ORACLE_SID = [wadhah] ? orclv2

5. Connecting Without a Password

Now connect using:

[wadhah@admin19c ~]$ sqlplus /

SQL*Plus: Release 19.0.0.0.0 - Production on Thu Sep 14 17:18:08 2025
Version 19.3.0.0.0

Copyright (c) 1982, 2019, Oracle.  All rights reserved.


Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0

SQL> show user
USER is "OPS$WADHAH"
SQL> exit
Disconnected from Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0

[wadhah@admin19c ~]$

Oracle automatically mapped:

Linux user: wadhah
Database user: OPS$WADHAH

No password required.