Read some questions about the enterprise application architecture model

1. Activation of the Mapper:
Fowler said that the er isolates the domain logic and database, and the domain logic and database will not perceive the existence of the er. So how to activate the er?
He said there are two ways: one is to build a third-party subsystem to complete the ing and the calling of the Er (that is, to create another service layer, and then the UI Layer calls this service layer ); one is to use the er as an observer in the domain logic or database.
How do you understand it?

2. Table module:
Is the table module applicable only to CS?ProgramIn the example, three tables are put in a dataset, and then the corresponding datatables are added, deleted, modified, and row-based.
If BS does the same thing, will it be depressing? You think, if there are tens of thousands of data records, the three tables will be 0.3 million pieces of data, all of which will be loaded, and it will slow you down, then, when the page is sent back, it is a big problem where such a large dataset is stored ......