Oracle 10g: Issue with startup mount command (ORA-24324, ORA-01041) - oracle

Question

I want to disable the archive logs in my oracle db. But when i shutdown and try to mount the database i am getting the following error.
C:\>sqlplus scott/tiger#ORCL as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Sep 18 10:44:17 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORA-12514: TNS:listener does not currently know of service requested in connect
descriptor
SQL> startup mount
ORA-24324: service handle not initialized
ORA-01041: internal error. hostdef extension doesn't exist
Can any one please help me in resolving this issue.
Edit1:- Listener.ora
# listener.ora Network Configuration File: E:\oracle\product\10.2.0\db_1\network\admin\listener.ora
# Generated by Oracle configuration tools.
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = E:\oracle\product\10.2.0\db_1)
(PROGRAM = extproc)
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = INHOS.dg.server.com)(PORT = 1521))
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))
)
)

Answer 1

Not sure if this is root cause, but after shutdown and before startup, try exiting and re-entering SQL*Plus.
First edit:
Ok, so, two different problems. The "hostdef extension doesn't exist" error happens when you try to startup from the same SQL*Plus session you shutdown from. Solution is to exit and re-enter SQL*Plus between shutdown and startup.
The ORA-12514 "Listener does not currently know of service requested in connect descriptor" is due to trying to remotely start (your SQL*Plus connect string is scott/tiger#ORCL as sysdba which specifies #ORCL) the instance, and the listener is configured only for dynamic service registration. If your listener is configured only for dynamic service registration, then trying to remotely start the instance will give you an ORA-12514. It's a bit of a catch-22. The problem is, until the instance is started, it can't register with the listener. If it's not registered with the listener, you can't start it up. There are two possible solutions:
You could add a static listener configuration to the listener.ora file and bounce the listener.
You could directly login as the Oracle software owner, to the server that the database is installed on, and set ORACLE_HOME and ORACLE_SID, then connect as / as sysdba.
Hope that helps.

Answer 2

ORA-24324 can mean that the database simply has not been started, and so the resolution would be to
first start the database and listeners (if any)