Say you have a Fibre disk in Solaris. that disk in in sun cluster, is a mirror in veritas to a second disk. now say that disk is removed before you remove it in veritas and on the system. so you have this disk just sitting there in solaris that does not really exist. just sitting there staring at you. Veritas lists the disk as error [since it no longer exists]. and you have removed it from the plex, but other wise have left the disk alone.
if scdidadm -C and devfsadm -C are not clearing the device. then you have two options. restart the service with -r for resetting the hardware. the other option update_drv -f sd forces the scsi driver to rescan everything.