I'm configuring Oracle Data Guard and I'm experiencing ORA-12638. I have the Oracle 19c database on a Windows Server 2019.

In the DR site, I can connect to the primary with no problem. But connecting from primary to the DR site is where ORA-12638 shows.

I found out that changing the




works but I can't do sqlplus / as sysdba in the DR site, and in DG Broker, "validate network configuration for all" fails because of an incorrect username/password, even though it is correct and I tried logging in like this:

sqlpus nolog/
enter username:sys as sysdba
enter password:

How can I resolve this issue?

1 Answer 1


There might be multiple reasons for ORA-12638:

  1. The credentials might be incorrect
  2. The network configuration between the primary and standby databases may be incorrect.
  3. The authentication method specified for the connection might not be supported or configured correctly on both the primary and standby databases.

You can further investigate alert file for better understanding of the error

Please do ask for more help if needed.

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