I take the approach of adding my .DFI items to a class that extends %DeepSee.UserLibrary.Container following

Creating a Business Intelligence Container Class

as this allows me to treat like any other class.

This means I can

• commit to the source control repository just like any other class
• deploy like any other class
• include the Container class in my module definition to be delivered via ZPM/IPM

This capability has been around since 2018 +/-.

and while not documented fully in DocBook the usage of %NOPARALLEL can be used to tell the optimizer not to use parallel processing.

If we look to what InterSystems provides as an application like Ensemble(Interoperability) or HealthShare we will find the class defintions exist in the ENSLIB or HSLIB namespace.  Then via Package mapping you will find that Interoperability enabled namespaces or HS enabled namespaces map the package definitions.  For example in the namespace HSEDGE1 we see

which says the classes from these packages are visible to the HSEDGE1 namespace.  

The data for the extent of these classes by default would live in the associated db for the namespace HSEDGE1.

In most cases the data for the extent is not mapped so as to live in a single univeral database but generally speaking it could be, although in the case iof the Ensemble/Interoperability and HealthShare data you shoud not do this.