In Dynamics 365 for Finance and Operations, document management supports Azure Blob and SharePoint online for saving record attachments. Database storage is not supported anymore.
Azure Blob: Azure Blob storage is the default storage for Dynamics 365 for Finance and Operations. It is equivalent to storage in a database, as documents can only be accessed through Dynamics 365 for Finance and Operations. Also, it provides the added benefit of providing storage that doesn't negatively affect the performance of the database.
SharePoint Online: When you have an O365 license and MS, autodiscover the SharePoint tenant, for example, a user on the packtPublication.onmicrosoft.com O365/AAD tenant gets packtPublication.sharepoint.com as the SharePoint site. This whole architecture allows SharePoint storage to work immediately.