SAP DB is the old name of SAP MaxDB.
As of database version 7.5, the former SAP DB database software is delivered under the name SAP MaxDB. SAP MaxDB 7.5 is the result of the continuing development of the SAP DB source code. SAP MaxDB 7.5 can be used as a direct upgrade for SAP DB versions as of 2.7.04. As per the releases for SAP applications, this also applies to SAP DB databases in SAP installations.