There are some unusual circumstances where you may not wish a higher-order service instance to synchronize with a lower-order service instance that currently holds server status. Typically, one workstation would be regarded as holding the master set of service data, regardless as to whether or not that service instance was running on that workstation. VTS Security Manager is just one such service.
When initializing or on change of server, servers of a lower-order than the active server will synchronize with the active server. Servers of a higher-order than the active server will not synchronize with the active server.
To achieve this, the service must pass a valid non-zero value in the PrioritySync parameter to the \RPCManager\Register call (see Service Control Methods).
This does not change the server evaluation rules or the synchronization sequence, it merely prevents synchronization with a lower-order server.