Oracle Database Express Edition (XE)

Hi all!

I am very new to Oracle and I am doing some selfstudy practice with Oracle XE.
I have tried to do some changes to the startup parameters. Ufortunatelly the database could not startup after this (I have than tried to recopy the 'pre-changes' spfile back...but I think I was too naive thinking it would work). Now I am getting (after beeing connected to an idle instance):


OS: XP Professional; Oracle DB XE

I have tried to change some parameters like: alter system set db_cache_size = 29360138 scope = spfile;

Now I am getting (after beeing connected to an idle instance):


ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist

neither startup nomount does not work.

I have tried also with:

startup spfile='C:\oraclexe\app\oracle\product\10.2.0\server\dbs/spfileXE.ora'

but I get SP2 0714: invalid combination of STARTUP options

and with startup command I get:

ORA-01078: failure in processing system parameters
ORA-00600: internal error code, arguments: [733], [538969660], [pga heap], [], [
], [], [], []


I have tried also to recreate the pfile from spfile and vice versa.

Services restarted and if I try Start->Programs->Oracle 10g Express Edition->Start database I don't get any errors.

If I check the alert_xe file it is pinting me to a trace, from which I am pasting a piece from my last startup attempt:

*** 2006-11-28 14:38:15.265
ksedmp: internal or fatal error
ORA-00600: internal error code, arguments: [733], [538969660], [pga heap], [], [], [], [], []
Current SQL information unavailable - no SGA.
.
.
.
----- Dump of the Fixed SGA -----
***** SGA not mapped *****
----- Dump of the Fixed UGA -----
***** no UGA *****
KSTDUMP: SGA no longer mapped
Dump event group for SESSION
Unable to dump event group - SGA not mapped
Dump event group for SYSTEM
Unable to dump event group - SGA not mapped



Unfortunatelly there is no backup of the database.

How can I startup DB again? Thanks for help and patience.

regards,
Peter