In lte, an UE can attach to network either combined or eps attach.
In case of combined attach, UE context is created at SGSN as well as MME.
Now if UE context is removed from either of one the nodes, Partial Purge UE procedure is being executed towards HSS.
PUR-flag within the Purge-UE-Request message carries the information that is related to Partial Purge of Ue.