How to connect Oracle 18c server using oracle 10g server

Question

While connecting Oracle 18c using oracle 10g I am getting error like "ORA-28040: No matching authentication protocol exception". I can able to connect "SQL DEVELOPER" but not able to connect "Command prompt"

Answer 1

Oracle documentation says:

Connections to Oracle Database from clients earlier than release 10g fail with the error ORA-28040: No matching authentication protocol.

Starting with Oracle Database 18c, the default value for the SQLNET.ALLOWED_LOGON_VERSION parameter changes from 11 in Oracle Database 12c (12.2) to 12 in Oracle Database 18c. The use of this parameter is deprecated.

SQLNET.ALLOWED_LOGON_VERSION is now replaced with the SQLNET.ALLOWED_LOGON_VERSION_SERVER and SQLNET.ALLOWED_LOGON_VERSION_CLIENT parameters. If you have not explicitly set the SQLNET.ALLOWED_LOGON_VERSION_SERVER parameter in the upgraded database, then connections from clients earlier than release 10g fail with the error ORA-28040: No matching authentication protocol.

See if it helps.

Answer 2

In 18c the default minimum version has been changed from 11 to 12 and SQLNET.ALLOWED_LOGON_VERSION is deprecated and replaced with SQLNET.ALLOWED_LOGON_VERSION_SERVER and SQLNET.ALLOWED_LOGON_VERSION_CLIENT

set

SQLNET.ALLOWED_LOGON_VERSION_SERVER=10 
SQLNET.ALLOWED_LOGON_VERSION_CLIENT=10

in your sqlnet.ora and reload listener lsnrctl reload

Answer 3

It is not possible, see Client / Server Interoperability Support Matrix for Different Oracle Versions (Doc ID 207303.1)

Even if you set SQLNET.ALLOWED_LOGON_VERSION_... the connection will most likely fail with another error.