In general, a big schemas are supported, but I can recommend to split service with very big schema to several ones with logical division: e.g. different departments should use different services: logistic department should have no access to account deparment service, etc
also, in case of Delphi, whole schema is stored in _impl.dfm. so creating of service might be slower than in service with small schema.
In general, service schema is deserialized from its xml form once on application startup, so there is absolutely no performance hit at runtime regarding to the data service instantiation.
Data access performance also shouldn’t be affected - while it would take more time to find the objects in the schema while serving the request, this time is completely insignificant compared to the possible network delays, database access etc.
It heavily depends on what code you have in your Delphi-based server. F.e. in case the data service doesn’t contain any custom code migrating to .NET will be as simple as:
Prepare the Schema to migration:
Copy the .daSchema and .daConnection files to other location
Open them using Schema Modeler
Edit the connection strings - they should use .NET drivers, not Delphi ones.
Create a new .NET server app using Wizard (use the sample database connection)
Replace the .daSchema and .daConnection files in the server app project folder with ones created on the previous step
At this point the app should be able to run and to server data requests. Further steps would require migrating authentication logic to .NET, additional functionality migration etc.
Our support team will be happy to help you with any issues in case they arise.