Visual FoxPro provides two processing modes for retrieving and updating remote data using SQL pass-through: synchronous and asynchronous. When you use SQL pass-through functions you can choose the method you prefer. You don't need to choose a method for remote views; Visual FoxPro automatically employs progressive fetching and manages the processing mode for you for remote views.
Benefits of Synchronous Mode
By default, Visual FoxPro SQL functions are processed synchronously: Visual FoxPro doesn't return control to an application until a function call is completed. Synchronous processing is useful when you're working with Visual FoxPro interactively.
Benefits of Asynchronous Mode
Asynchronous processing provides greater flexibility than synchronous processing. For example, when your application is processing a function asynchronously, your application can build a progress indicator to display the progress of the executing statement, display movement of the mouse pointer, create loops, and set timers to allow interruption of processing that is taking too long.