ORA28040 No matching authentication protocol SQLNET. ALLOWEDLOGONVERSIONSERVER. No matching authentication protocol SQLNET. ALLOWEDLOGONVERSIONSERVER Oracle 4. Ah, an old client is trying to connect to Oracle 1. Also ORA 0. 31. Connections to this server version are no longer supported can occur. This actually implies that the authentication protocols use between client and server do not match.  In Oracle 1. SHA 2 encryption algorithm by default, where older clients use SHA 1. So when an older client is used with defaults, the server will not accept the connection. The best option would be upgrading the client, but when older dlls are used like ojdbc. The database instance can be told to accept older clients and use the older SHA 1 encryption algorithm. SQLNET. ALLOWEDLOGONVERSIONSERVERThis is done in 1. SQLNET. ALLOWEDLOGONVERSIONSERVER option in the SQLNET. ORA in the database home not grid home. Using an older client or ojdbc. This section describes the connection URL format and how to create connection objects with the DriverManager class. I wrote a Java Servlet program but when I run it, it was showing the Exception java. lang. ClassNotFoundException oracle. jdbc. driver. OracleDriver My code is package. Your Take on Oracle JDBC Drivers NEW Get Oracle JDBC drivers and UCP from the Oracle Maven Repository NEW 9 JDBC ClientSide Security Features. This chapter discusses support in the Oracle Java Database Connectivity JDBC Oracle Call Interface OCI and JDBC Thin drivers. OracleMaven3Oracle JDBC driverMavenOracle JDBC driver,. Cisco Unified CCX Administration Guide, Release 10. 61 Subsystems Menu. Using the ojdbc. 6. Sorry, I did not test the ojdbc. Oracle says To set the minimum authentication protocol allowed when connecting to Oracle Database instances. When this parameter is set to 8, it permits most versions and allows any combination of the passwordvalues in DBAUSERS to be 1. G, 1. 1G, and 1. 2C. A SQLNET. ALLOWEDLOGONVERSIONSERVER setting of 1. C. Get your complete description about this parameter here SQLNET. ALLOWEDLOGONVERSIONSERVERSQLNET. ALLOWEDLOGONVERSIONCLIENTWhat about the SQLNET. ALLOWEDLOGONVERSIONCLIENT parameterAt first I thought this should be setting to be set, like which lowest client version is allowed, but that was not the case. Oracle says To set the minimum authentication protocol allowed for clients when connecting to Oracle Database instances. According to the documentation, it seems this is used for database links. If you want to connect from 1. SQLNET. ALLOWEDLOGONVERSIONCLIENT must be set to 1. SQLNET. ALLOWEDLOGONVERSIONThe older SQLNET. ALLOWEDLOGONVERSION parameter is deprecated from alert. Using deprecated SQLNET. ALLOWEDLOGONVERSION parameter. Happy connecting