监听器启动，并不一定会认识数据库实例，启动监听器，请判别相关实例是否 READY

[oracle@redhat4 ~]$ lsnrctl status

LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 06-OCT-2015 19:41:12

Copyright (c) 1991, 2009, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 11.2.0.1.0 - Production
Start Date                06-OCT-2015 16:24:17
Uptime                    0 days 3 hr. 16 min. 55 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /u01/app/oracle/product/11.2.0/dbhome_1/network/admin/ listener.ora
Listener Log File         /u01/app/oracle/diag/tnslsnr/redhat4/listener/alert/lo g.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=redhat4.7)(PORT=1521)))
Services Summary...
Service "ora11g" has 1 instance(s).
  Instance "ora11g", status READY, has 1 handler(s) for this service...
Service "ora11gXDB" has 1 instance(s).
  Instance "ora11g", status READY, has 1 handler(s) for this service...
Service "orcl.7" has 1 instance(s).
  Instance "orcl", status READY, has 1 handler(s) for this service...
Service "orclXDB.7" has 1 instance(s).
  Instance "orcl", status READY, has 1 handler(s) for this service...
The command completed successfully
-------------------------------------------------------------------------------------------

[oracle@redhat4 ~]$ sqlplus system/oracle@ora11g

SQL*Plus: Release 11.2.0.1.0 Production on Tue Oct 6 19:46:33 2015

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> alter system register;

System altered.

SQL> exit;
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@redhat4 ~]$ sqlplus system/oracle@orcl

SQL*Plus: Release 11.2.0.1.0 Production on Tue Oct 6 19:47:25 2015

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> alter system register;

System altered.