Most SAP Business One systems are still being used in combination with a Microsoft SQL Database operated. However, in the future there will be more and more installations with HANA, SAP's high-performance database.
There is already quite a bit of literature, but there are now also plenty of resources on the Internet where you can find know-how on SAP HANA can obtain.
One possibility is the English-language website SAP HANA Central. Here you can find many tutorials and learning material on the SAP In Memory database.