Oracle9i以后，后台进程PMON自动在监听器中注册在系统参数SERVICE_NAMES中定义的服务名，SERVICE_NAMES默认为DB_NAME+DOMAIN_NAME。监听配置文件listener.ora中可以不必指定监听的服务名。但是，当数据库处于关闭状态下PMON进程没有启动，也就不会自动注册监听的实例名，所以使用sqlplus sys/his@orc0 as sysdba 会出现ORA-12514错误。
Title: TNS:listener does not currently know of service requested in connect descriptor
TNS:listener does not currently know of service requested in connect descriptor
- Wait a moment and try to connect a second time. - Check which services are currently known by the listener by executing: lsnrctl services <listener name> - Check that the SERVICE_NAME parameter in the connect descriptor of the net service name used specifies a service known by the listener. - If an easy connect naming connect identifier was used, check that the service name specified is a service known by the listener. - Check for an event in the listener.log file.
The listener received a request to establish a connection to a database or other service. The connect descriptor received by the listener specified a service name for a service (usually a database service) that either has not yet dynamically registered with the listener or has not been statically configured for the listener. This may be a temporary condition such as after the listener has started, but before the database instance has registered with the listener.