This article describes how to modify the resource dependencies in the cluster.
Some time back i dropped a diskgroup DG1 from the SQL prompt and it is dropped successfully without any errors. But when i see the cluster resources status, the diskgroup resource still displays in offline status. Further investigations revealed that the disk group details still exist in OCR.
When i try to restart the database, it gives the error CRS-2640. I tried to delete the OCR details as well with srvctl command and able to delete the OCR details. Tried again to start the database but failed with error. The work around to this error is to modify the OCR with the existing diskgroups.
Hope it helps