To define TSO/E address spaces to VTAM®, use VTAM APPL definition statements. You must code one APPL definition statement to define the primary TSO/E address space, and at least as many APPL definition statements as there will be users logged on to TSO/E at one time. For example, if you want to allow 50 users to use TSO/E simultaneously, code 51 APPL definition statements: one for the primary TSO/E address space and one for each user address space. You might want to code more APPL definition statements than you currently need, to accommodate users you plan to add to your system later. For more information about using the APPL definition statement, see and .