有时候会遇到下面的这个错误
LSNRCTL> save_config
Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
NL-00051: internal error code, arguments: [302], [1], [], [], [], [], []

原因为没有listener.ora文件导致.

出现问题的过程如下:
[oracle:/home/oracle#]lsnrctl

LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 16-4?? -2011 15:02:14

Copyright (c) 1991, 2005, Oracle. All rights reserved.

Welcome to LSNRCTL, type "help" for information.

LSNRCTL> start
Starting /opt/ora10g/product/10.2.0/db_1/bin/tnslsnr: please wait...

TNSLSNR for Linux: Version 10.2.0.1.0 - Production
Log messages written to /opt/ora10g/product/10.2.0/db_1/network/log/listener.log
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=localhost.localdomain)(PORT=1521)))

Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 10.2.0.1.0 - Production
Start Date 16-4?? -2011 15:02:15
Uptime 0 days 0 hr. 0 min. 0 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Log File /opt/ora10g/product/10.2.0/db_1/network/log/listener.log
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=localhost.localdomain)(PORT=1521)))
The listener supports no services
The command completed successfully
LSNRCTL>
LSNRCTL>
LSNRCTL> change_password
Old password:
New password:
Reenter new password:
Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
Password changed for LISTENER
The command completed successfully
LSNRCTL> save_config
Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
NL-00051: internal error code, arguments: [302], [1], [], [], [], [], []
LSNRCTL>

对于这类问题的解决方法:
如果能够使用图形化界面登陆的话,可以使用netca来创建listener.ora文件.
如果不能使用图形化界面,直接在$ORACLE_HOME/network/admin目录下创建一个listener.ora文件,即使是一个空的文件也可以.

另外在Windows上测试的时候,不能修改Oracle listener的密码,只能首先将listener.ora文件中的密码部分注释掉,然后创建新的密码才可.