Clustered Netbackup 7.6 Master Servers uses undocumented link that will cause issues when performing catalog restore, if the nbu_server resource is either stopped or failed state.
VCS creates a link upon startup from /usr/openv/var/global to /opt/VRTSnbu/var/global and removes it again when nbu_server resource is offlined.
Before performing any restores of the NBDB/EMM database create the link manual:
# cd /usr/openv/var
# ln -s /opt/VRTSnbu/var/global global
Catalog restores will then work according to the manual in the troubleshooting normal.