Before upgrading to Release 7.1.0 release, you must have no sessions in the /var/log/sonus/evlog/ or /var/log/sonus/evlog/evlog/ directories.
/var/log/sonus/evlog/
/var/log/sonus/evlog/evlog/
(This Note does not apply if you are upgrading from 6.2.2, 7.1.0 or later versions.)