rdisp/max_vb_server is a SAP Parameter attribute which is used to control Maximum number of update servers 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 .
rdisp/max_vb_server configures the maximum number of update servers that
can be used to dispatch update requests.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.