Central User Administration 

An SAP system group consists of several SAP Systems with several clients. The same users are frequently created and maintained in each client.

Using central user administration, you can maintain these users centrally in one system. The information is then automatically distributed to the dependent systems.

For more information, see:

Setting Up Central User Administration

Setup distribution field distribution parameters

Migration of existing users into the central system

Central user distribution

Distribution Logs

Global User Manager