ORA-01041 : internal error. hostdef extension doesn't exist.

What does it actually mean?
What is the hostdef extension?

Solution Description:
=====================


The hostdef extension referred to is a structure which was added to the control
structure for the client/server communication.


It is accessed via a pointer in the original structure.
When the communication between the client and the server goes awry, this can
result in ORA-1041 and ORA-3113 errors.


The ORA-1041 is flagged when the POINTER to the EXTENSION structure for the
HOST DEFinition (for the communication channel between the client and the
server) has been nulled. This can occur when the connection gets lost 'for some
reason' and hence the procedure to investigate is the same as for ORA-3113.


Explanation:
============


The hostdef extension refers to the structures used to maintain the
client/server communication channel.

This problem typically occurs when you don't have your environment set up correctly.

Try to drop the database with the DBCA and recreate it again. This will also set up your environment. See if that helps. If it doesn't, then you have to solve the ORA-3113 error. This is quite a lengthy topic, so I'll refer to your Oracle Support's discussion. Go to Metalink and look up Note 19790.1. It discusses how to solve ORA-3113 errors.