Module pools are executed in a very different manner than executable programs. Executing a module pool does not start a process in the runtime environment that sends events to the ABAP program in a specified sequence. Neither can module pools be started by entering their name or using SUBMIT. Transaction code To start a module pool you need to create at least one screen and define a transaction code, which is linked to one of the module pool screens. This screen then becomes the initial screen of a transaction with the ability to call other screens of the module pool.