Random selection determines which elements are to be counted from every stratum. When you perform the random selection, any previous actions become binding. Stock management levels, stock population and stratification can no longer be changed. A session for physical inventory documents is automatically created during the random selection process. You can also choose if the physical inventory is to be performed (in which you run the session), or not. Random selection occurs with the help of the random numbers that are created in the SAP System by an internal random number generator.