ORA-01034: solutions to ORACLE not available Problems

The newly installed oracle9i can still be used last time. This time it suddenly won't work.

[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) 1982,200 2, Oracle Corporation. All rights reserved.
ERROR:
A 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) 1991,200 2, 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) abve...

[Oracle @ R39i oracle] $ lsnrctl status

LSNRCTL for Linux: Version 9.2.0.4.0-Production on 24-NOV-2008 11:21:13

Copyright (c) 1991,200 2, 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) 1991,200 2, 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

The listener has been started.
[Oracle @ R39i oracle] $ sqlplus/nolog

SQL * Plus: Release 9.2.0.4.0-Production on Mon Nov 24 12:01:37 2008

Copyright (c) 1982,200 2, 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.

The database can be used.

Conclusion,

1. When the database is not opened, other users cannot be connected.
2. If sys cannot open the database, it may be a bad environment variable.

You can use the following method to check whether it is the same as you expected.

Env | grep ORACLE