Thanks vbe for your help.
I think I have now found the cause of my problems.
After restoration I have the socket file /var/opt/OV/sockets/lic.unixstr present.
It seems that this file needs to be removed and the server rebooted for the licensing to work.
After reboot the socket/file is recreated and the Openview licensing works.
I am unsure why restoration of the server1 backup worked when the server0 restoration did not. But the removal of this file definitely solves all the problems.
I have since found that there is a patch PHSS_15728 which states " After installing patches PSOV_01688 and PSOV_01863 it is necessary to rm /var/opt/OV/sockets/lic.unixstr for licensing to work."
However, this patch seemed to apply to Unix versions 10.xx whereas my Unix version is B.11.00
It is possible that this problem re-occurred later and required a patch which we don't have and now cannot find as this OS is now not supported.
Anyway... this was definitely the problem and everything is now sorted.
Thanks for all your help !
Clive
