Hi Valeri,
when upgrading MDS, there is no need to recreate the VSX, as the version of the VSX stays the same, and the object in the mgmt DB are updated as part of the mgmt upgrade, similar to SGW objects.
when upgrading the VSX itself, there is also no need to recreate the VSX. the procedure should be:
1. upgrade the mgmt db using vsx_util upgrade
2. run cpuse upgrade on the gw (if you have a vsx cluster, use CU procedre to preserve connections between the members)
both vsx_util upgrade and cpuse upgrade preserve the existing configurations
if the migration preserve the same domain names and IPs, the new mgmt will work seemly with the old VSX. if there is a change in domain name or IP, you can recreate the VSX automatically with the vsx_util reconfigure command from the new domain