one of the VDX 6740t switch in the logical chassis had partition corrupted. Brocade sent me a replacement. I followed the instruction provided here http://www.brocade.com/content/html/en/administration-guide/nos-701-adminguide/GUID-FD3B87D5-E2F5-4C1A-A01C-4061ED597857.html
When I did #show vcs from the principal switch , the status showed replacing and unknown.
#show fabric islports, ISL ports had ESC distributed Config DB Conflict error
Solution:
1. Shutdown the all the ISL ports on the new/replacement switch.
2. #copy default-config startup config