SAPLOCALHOSTFULL is a SAP Parameter attribute which is used to control Provides host+domain name. 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 .
This parameter provides the host name, including the full domain name,
of the currently-used system.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.