Storage array shows error 'KAIC06400-E' while unmapping the LUN

Issue

• We removed couple of SAN devices from the system using steps in KCS -3941 but when trying to unmap these disks at storage level we are getting below error

  Error on storage array console:

  An error occurred during storage system processing. (error code 1 = "1005", error code 2 = "2082", meaning = "Processing is disabled because the host is mounted or the device is reserved. Unmount the host and cancel reservation of the device. If the host is an AIX host,  unmount the host, and execute the varyoffvg command.") If the configuration was changed, refresh the storage system information. If you do not have the permissions required to refresh the information, ask the storage system administrator to do it for you. (KAIC06400-E)
  

• The same error continues even after rebooting the Linux systems to which the LUNs were previously assigned.