login/multi_login_users is a SAP Parameter attribute which is used to control list of exceptional users: multiple logon allowed information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
This list contains the R/3 logon names (ignoring the client) of users
who are permitted to log on to the system more than once.
(Caution: Special input format, see below)
This profile parameter applies to dialog users only.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.