Ah, the penny just dropped: you said before "In CCM, I am selecting 'specify CMS data source' option and then selecting 'select a Data source'". This process means that yuo have told the CMS that from now on, it should no longer read and write to the previous database, but should now use this new database location. Of course, this is fine - as long as you realize this will be an empty database. As the CMS starts, it will create the necessary tables and some default users (like the administrator, which now no longer has a password).
So you want your old data back? Then I hope the old Oracle 10 database is still running. Go to CCM > Specifiy CMS data source > Sleect copy datasource. Now enter the details of the old Oracle 10 schema for the source and the new Oracle 11 schema for the destination and a few minutes later (depending on the size of your database) your data will have been transferred. Restart your CMS and login again with your old user administrator password and you should see the old data.
Does that work?