在startup 启动数据库后，使用plsql去连接数据库时，
出现ora-12170 错误:
在启动、关闭或者重启oracle监听器之前确保使用lsnrctl status命令检查oracle监听器的状态：
1、$lsnrctl status：检查当前监听器的状态
2、$lsnrctl start [listener-name] 启动所有的监听器,可以指定名字来启动特定的监听器
3、$lsnrctl stop [listener-name] 关闭所有的监听器，可以指定名字来关闭特定的监听器
4、$lsnrctl reload 重启监听器，此命令可以代替lsnrctl stop,lsnrctl start
5、lsnrctl hep 可以显示所有可用的监听器命令
常用命令参数：
start - Start the Oracle listener
stop - Stop the Oracle listener
status - Display the current status of the Oracle listener
services - Retrieve the listener services information
version - Display the oracle listener version information
reload - This will reload the oracle listener SID and parameter files. This is equivalent to lsnrctl stop and lsnrctl start.
save_config - This will save the current settings to the listener.ora file and also take a backup of the listener.ora file before overwriting it. If there are no changes, it will display the message “No changes to save for LISTENER”
trace - Enable the tracing at the listener level. The available options are ‘trace OFF’, ‘trace USER’, ‘trace ADMIN’ or ‘trace SUPPORT’
spawn - Spawns a new with the program with the spawn_alias mentioned in the listener.ora file
change_password - Set the new password to the oracle listener (or) change the existing listener password.
show - Display log files and other relevant listener information