Installing/Updating with SDBINST 
You
are installing or updating all
components of the
SAP DB Software on the Linux operating system.
If you only want to install or update individual components, you must consider
the dependencies between SAP DB components to ensure that the software
installation can function. For more information, see the
Installation Guide:
SAP DB 7.4.

If you already have a SAP DB installation on your host that was installed using the Red Hat Package Manager (installation with an rpm package), you can only perform additional installations or updates using this program.
It is no longer possible to perform additional installations or updates using the SDBINST program (installation with a tgz package).
Follow the procedure described in the section Installing/Updating Under UNIX.