rdisp/vbdelete is a SAP Parameter attribute which is used to control Delete old update requests 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 parameter specifies the duration in days after which an update
request is deleted. After this duration has expired, the update requests
are deleted irrespective of their status. If the parameter has the value
0, the update requests are not deleted.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.