In z/OS®, three factors determine the maximum numbers of users who can be logged onto TSO/E concurrently: the number of available logons, the number of address spaces that can execute concurrently, and the number of VTAM® APPL definition statements defined to VTAM. The smaller of these three factors limits the number of concurrent logons. You should examine, and if necessary, adjust these factors to meet your installation's needs.

If you need to further control or limit logons, you can define groups and assign TSO/E users to these groups. You can then write a logon pre-prompt exit routine that allows or disallows a user to log on based on the group to which the user is assigned.

For more information about limiting concurrent logons, see Setting up logon processing.