You can validate the Business Continuance plan at any time; however, you should validate it at fixed intervals, especially before starting the failover process. This ensures that correct resources and server configuration get involved in the recovery operation.
If the mountpoint root LUNs required for recovery are not a part of the BC plan and do not exist on the BC host, the BC plan validation and execution fails. To avoid such failures, ensure either that such LUNs have Exchange or SnapManager SnapInfo directory components in them or that the mountpoint root LUNs are connected to the BC host prior to running the validation.