A BS2000 user ID is identified under POSIX via the user number. For this reason, a user number must be allocated to every BS2000 user ID who wants to use POSIX (see "Defining default values for POSIX user attributes"):
Every existing BS2000 user ID is automatically assigned the default user number for a first start or for version upgrade.
Every new BS2000 user ID receives the default user number when it is defined.
As a result, there is a large number of BS2000 user IDs which all have the same default user number.
POSIX administrators and BS2000 system administrators can determine the value of the default user number with the BS2000 command /MODIFY-POSIX-USER-DEFAULTS. They must also assign an individual user number to each BS2000 user ID in place of the default user number before POSIX can be used under this BS2000 user ID. The command for this purpose is /MODIFY-POSIX-USER-ATTRIBUTES. A warning is displayed if a user number is repeatedly assigned, except in the case of the default user number.
User numbers from 0 to 99 are reserved for privileged users (system IDs). User numbers from 100 are kept for nonprivileged users.
Different BS2000 user IDs with the same user number are mapped to the same POSIX user ID. However, the BS2000 user ID and the user number are independent of each other.
Unequivocal allocation of BS2000 user IDs and user numbers is particularly important in a computer network with UNIX systems, since consistent user identification based on user numbers is required for all computers and systems in the network.