https://www.dell.com/support/kbdoc/en-us/000204844/unisphere-for-powermax-when-removing-a-device-from-an-sg-the-srdf-relationship-is-deleted
Removing a device from a storage group (SG) deletes the Symmetrix Remote Data Facility (SRDF) relationship.
unispherepowermaxsrdfrelationshipdeleted