Well the definition varies from vendor to vendor.
in one vendor directed retry DR is when you are using a feature also assisted by MSC to wait for some time before channel assignment when no resource is available on the cell and cause a HO to a TCH assigned on another cell.
Forced_DR may be enabled without the MSCs assistance and in I think Alcatel there is also a difference that DR uses the margin equal to that of PBGT HO and Forced HO has its own margin which might be different.