How do I add users? Do I have to add them all to each client one-by-one?

You use transaction SU01 to add and change users. If you want to copy the users from client 100 to the users in client 110, you can do a special kind of client copy that is non-destructive. When the profile SAP_USER is used during a client copy, just the user master data is copied from the source client over the target client, and the rest of the database is left intact.

No matter how you manage your user security, there is no getting around the fact that you have to manually add them all to at least client at some time or another. The best way is to add them all to client 100 in DEV since that is the “Golden” client and should never be “refreshed” or written over by a client copy. Once you have them all in one spot, you can use a client copy for just user master data and pop all the clients wherever you want them.

There is another way to add users to clients called Central User Administration (CUA). CUA allows you to designate one client in the SAP landscape that is the parent of all or specified clients, both local and remote. When you add a new user to the parent client, the child clients get populated with this data. Thus, one user add will trigger others within the instance and to other SAP instances as well. This technique should only be used on clients that are not to be refreshed in the future.