rdisp/rpag_file is a SAP Parameter attribute which is used to control Name of paging file 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 .
Name of paging file (with path). This file must exist as it is used by
the SAP system to save user data, for example, lists.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.