codepage/R2host is a SAP Parameter attribute which is used to control Specify codepage of R2 system / used by R2 sapgui 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 is only used for the CUA interface (logon with SAPGUI to
R2 used) and specifies the codepage used by the R2 system for
ASCII/EBCDIC character conversion.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.