Use the international standard database engines as the content and configuration database

Hi,

My potentially future project on AEM should have the ability to use the international standard database engines as the content and configuration database , such as DB2, Oracle, Microsoft SQL.

I am aware that AEM connects with databases for CRUD operations , but my question is whether  AEM could have a database at the storage layer, as opposed to JCR/ Mongo DB?

Appreciate your replies.

Thanks,

Rama.