rspo/local_print/server is a SAP Parameter attribute which is used to control Server used for frontend printing 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 .
If this parameter is defined and not empty, it defines which server
(with at least one spool work process) is to be used to process output
requests using access method "F" (front-end printing). Logical server
names can be used in addition to real servers. Alternative servers are
considered. If no server is defined explicitly, the local server is used
if it has at least one spool work process. Otherwise, a server with a
minimum load is selected for the processing out of the spool servers
available in the system.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.