SAPTRANSHOST is a SAP Parameter attribute which is used to control central host for transports (Windows only) 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 .
SAPTRANSHOST can be specified in DNS or in the local hosts. This means
that the DIR_TRANS parameter in the profile or transdir can be omitted
in the TPPARAM.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.