rdisp/vb_context_sep is a SAP Parameter attribute which is used to control Separator for update context info 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 .
The update context is used to distribute update requests. It consists of
the pair (installed languages, DB group). An update request can only be
sent to an update server if the update server belongs to the same DB
group and the relevant language is installed there. This parameter
configures the character that is used to separate the two specified
values. By default, this is the character ':'. However, if this
character also occurs in the vector of the installed languages, you need
to use a different value.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.