Hi Shazin,
Can you try one thing:
1. Install BO with default database and check whether SIA is getting created.
2. If SIA is created, stop the SIA --> right click and select properties --> Configuration tab --> in CMS database button click Specify and select Copy To radio button and select the default database as Source and Oracle DB as destination. It will take some time to perform this step. After that is successful, BO will be pointed to Oracle.
Thanks,
M.Sumesh