Hi Dave,
I haven't done it myself, but I guess you could use the pg_dump/pg_dumpall/pg_restore/psql commands from /opt/vmware/vpostgres/1.0/bin/ within the appliance.
Please beware that in addition to VRMS database, there are also an embedded (SQLite) database for VR server, configuration files and key pairs within the appliance.
Backing up only the VRMS database won't help in the event of losing the replication appliance.
You could perform some backup of the whole appliance.
There is no official tool yet for VRMS database migration, but the feature has been requested and might become available in some future release.
Regards,
Martin