install/uid is a SAP Parameter attribute which is used to control User identification used by whole R/3 towards the operating system 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 .
Most operating systems have a concept of different users. But when an
R/3 system is started, the whole system is handled like a single program
and is associated with the user (on operating system level), who started
R/3.
This profile parameter specifies which user should be used to start R/3.
If you use a different user, this affects most of R/3's operations.
But there are some exceptions:
An SAP program running under an identification other than the one in
this parameter will never create a SCSA on its own. If there is no SCSA
and the profile value of
See SAP Parameter Documentation for full SAP documentation for this profile parameter.