The user name is assigned a user master record and
authorizations that modify
the behavior of an ABAP program. The current user name is returned by the method GET_USER_NAME of the class CL_ABAP_SYST and can be fetched from the
system fieldsy-uname.
The client ID determines the current client. When database content is accessed using
ABAP SQL,
implicit client handling is used by default
and only the data of the current client is accessed. The current client is returned by the method GET_CLIENT of the class CL_ABAP_SYST and can be fetched from the
system fieldsy-mandt.
The logon language determines how various text repositories are accessed and is the
text environment language
by default. The current logon language is returned by the method GET_LOGON_LANGUAGE of the class CL_ABAP_SYST. The
system fieldsy-langu, on the other hand, contains the text environment language of the current
internal session, which can be set to a different value.
There are various types of user sessions and various rules and restrictions apply when ABAP programs are executed: