[oracle@R39i oracle]$ sqlplus scott/tiger
SQL*Plus: Release 9.2.0.4.0 - Production on Mon Nov 24 11:06:50 2008
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux Error: 2: No such file or directory
[root@R39i root]# id oracle
uid=500(oracle) gid=501(dba) groups=501(dba)
[root@R39i root]# su - oracle
[oracle@R39i oracle]$ lsnrctl start
LSNRCTL for Linux: Version 9.2.0.4.0 - Production on 24-NOV-2008 10:57:29
Copyright (c) 1991, 2002, Oracle Corporation. All rights reserved.
Starting /oracle/product/9i/bin/tnslsnr: please wait...
TNSLSNR for Linux: Version 9.2.0.4.0 - Production
System parameter file is /oracle/product/9i/network/admin/listener.ora
Log messages written to /oracle/product/9i/network/log/listener.log
Error listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC)))
TNS-12542: TNS:address already in use
TNS-12560: TNS:protocol adapter error
TNS-00512: Address already in use
Linux Error: 98: Address already in use
Listener failed to start. See the error message(s) above...
[oracle@R39i oracle]$ lsnrctl status
LSNRCTL for Linux: Version 9.2.0.4.0 - Production on 24-NOV-2008 11:21:13
Copyright (c) 1991, 2002, Oracle Corporation. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC)))
STATUS of the LISTENER
==============================================
[oracle@R39i oracle]$ lsnrctl status
LSNRCTL for Linux: Version 9.2.0.4.0 - Production on 24-NOV-2008 11:21:13
Copyright (c) 1991, 2002, Oracle Corporation. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 9.2.0.4.0 - Production
Start Date 24-NOV-2008 10:52:27
Uptime 0 days 0 hr. 28 min. 45 sec
Trace Level off
Security OFF
SNMP OFF
Listener Parameter File /oracle/product/9i/network/admin/listener.ora
Listener Log File /oracle/product/9i/network/log/listener.log
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=R39i)(PORT=1521)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
Service "mydata" has 1 instance(s).
Instance "mydata", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully
呵呵，原来监听已经启动了.
[oracle@R39i oracle]$ sqlplus /nolog
SQL*Plus: Release 9.2.0.4.0 - Production on Mon Nov 24 12:01:37 2008
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
SQL> connect /as sysdba
Connected to an idle instance.
SQL> startup
ORACLE instance started.
Total System Global Area 122754448 bytes
Fixed Size 451984 bytes
Variable Size 88080384 bytes
Database Buffers 33554432 bytes
Redo Buffers 667648 bytes
Database mounted.
Database opened.
数据库就可以用了。
总结，
1,数据库没有打开时，其它用户是联不上的。
2,如果用sys也打不开数据库，则可能是坏境变量的事了。
可用下面的方法来检查,看是否和你预想的一样。
env |grep ORACLE