問題重現：
在虛擬機環境上安裝Oracle 12c數據庫後，配置好監聽，啓動好數據庫，在Windows上遠程連接數據庫報錯：ORA-28040
解決方法：
在$ORACLE_HOME/dbs/network/admin/下修改sqlnet.ora文件，在最後面新增如下內容：
SQLNET.ALLOWED_LOGON_VERSION=8
如圖：
解決思路：
[oracle@localhost dbs]$ oerr ora 28040
28040, 0000, “No matching authentication protocol”
// *Cause: There was no acceptable authentication protocol for
// either client or server.
// *Action: The administrator should set the values of the
// SQLNET.ALLOWED_LOGON_VERSION_SERVER and
// SQLNET.ALLOWED_LOGON_VERSION_CLIENT parameters, on both the
// client and on the server, to values that match the minimum
// version software supported in the system.
// This error is also raised when the client is authenticating to
// a user account which was created without a verifier suitable for
// the client software version. In this situation, that account’s
// password must be reset, in order for the required verifier to
// be generated and allow authentication to proceed successfully.