Oracle Database Discussions

Hello
I'm trying to migrate my database from 10g Oracle Express to 11g, they both are on a Windows 2003 server. The easiest solution that occured to me was the following:

1)To backup the 10g database: (this will restore the tables and data)
RMAN> connect target;
2>backup incremental level 0
3> as compressed backupset database;

2) I create the application (database schema and tablespace) on the 11g.

3) Copy the bak file generated on step 1) to the flashrecovery area autobakup of the 11g server.

4) Restore it in the 11g database:
RMAN> connect target:
2> shutdown inmediate;
3> connect target;
4> mount database;
5> configure controlfile autobackup off;
6> restore database;


My problem is that this doesn't work. I got the following errors:
-For step 1) and 2) I didn't have problems and the backup file was generated.
-On the step 4) on the 4th line the following errores are shown:
"could not obtain a fully authorized session (RMAN-06403)"
"ORACLE not available (ORA01034)"
"shared memory realm doesn't exist (ORA-27101)"

NOTE: If I enter to SQL+ or the Oracle Enterprise Manager, I can see that my database is up. After running line 4> my database is down and I have to configure everything back again.

If I skip lines 2>,3>,4> and execute inmediatly 5> and 6> the following errores appears (I already try it with on and off):
"RMAN-06023 no backup or copy of datafile [1,2,3,4] found to restore"

Could you tell me please, which is the the easiest way to migrate from 10g Oracle Express to 11g and what I'm doing wrong in the backup 10g and restore on 11g process? Thankyou.