-- FIRST IDENTIFY THE CORRECT SID by querying v$instance
1. do a clean / normal shutdown ( NO shutdown abort / immediate)
2. take a complete cold backup.
3. change the entries for ORACLE_SID in all .profile variables in any env settings
4. in unix goto $ORACLE_HOME/dbs and rename or create a new init< new_sid >.ora
   in windows , i beleieve it will be in $ORACLE_HOME/database or whereever the
   init file is.
   Make sure,all the entries in this new inti< new_sid >.ora are pointing
   to the new_sid.
   take care, if you are using spiles or oracle password files.
5. now mount and open the database using the new init_sid.file
   Check the functionality.
   u will see that, still the oracle files will be in old_sid as per OFA ( if u have used it)
   optionally, rename the datafile to point to a OFA structre for new oracle_sid