We need to upgrade the disk capacity of one of our secondary disks ( not boot disk ).For this we execute the follwoing steps: 1.Remove the entry from /etc/vfstab. 2.shutdown 3.Take the disk out. Its all so simple till here. We startup the machine.Format command does not show the disk any more. But, We still see the disk if we do 'ls -lt /dev/dsk/*'.Also prtconf mentions a disk to still exist in that particular slot. Now the question is: 1.Is this because we did not a reconfiguration boot after removing the disk. 2.If we would insert the new disk in the same slot and provided that the system has the appropriate drivers ; do we need to do a configuration boot at all?Or the existing logical mapping should work fine with the new disk too? Any help would be much appreciated.

Yes, you're probably seeing it because you didn't do a reconfiguration boot. I haven't encountered what you have before, but essentially any time you add/take out a hw component, you should do a reconfiguration boot so that Solaris reads in the new configuration. Could be asking for unwanted troubles if you don't. As for your second question, I am not sure, but I wouldn't take the chance (never know) You're probably familiar with how to do a reconfiguration boot, but just in case, here's a link I found.... http://www.boran.com/solarisdigest/solaristips20001220.html#boot

Put the new disk in and do a boot -r

You could also use 'devfsadm' to rebuild a configuration.