The system variable *USER is derived from USER.
Database stamping attributes are derived from USER.
PSUS, ASUS, PSPW and ASPW will be automatically converted to uppercase when attempting to connect to an IBM i server system. For non-IBM i server systems their case is unchanged.
When PSTC=Y, that is you have directed LANSA to use Windows Authentication (also called Trusted Connections), LANSA will firstly attempt to obtain the value of USER by looking up the Windows authenticated user in file LX_FKU. If one is found then USER is assigned the value of the associated PC User ID. Any existing value of USER is overwritten. If one is not found, then the defaulting logic below is used. This lookup always occurs when PSTC=Y. That is, it's not just performed when USER is unassigned.