Oracle Database Discussions

I have inherited an oracle 10g database on Windows and I need to set up RMAN backups. I am going through the steps and I think I am still missing something.

I am trying to put the database in archivelog mode and it gives me this error:

ORA-01126: database must be mounted in this instance and not open in any instance

So I try to mount the database (alter database mount;) and it says:

ORA-01100: database already mounted

So I figure someone else has it open so I shut it down (shutdown immediate), which works fine, but when I try to restart it (startup mount;) it tells me:

ORA-24324: service handle not initialized
ORA-01041: internal error. hostdef extension doesn't exist

So I try to log into a new session and it tells me:

ORA-12514: TNS:listener does not currently know of service requested in connect descriptor

The only way I can find to restart it is to restart the service OracleServiceDATABASENAME. When it is restarted, it lets me log in, but then I get the same errors as above when I try to mount the database or put it in archivelog mode.

Please let me know what I am missing.

Thanks!