What are `sync primaries, `sync backups, and `sync alternates ?
AIn a clustered environment, the primary is the server that holds authoritative session data for all application components that are marked for distributed sessions. Any such component will retrieve its data from the primary, and not from its own memory. If session data on a primary changes, the changes are reflected on the backups. This means that any backup can immediately become a primary if the primary fails; but no session data is obtained from backups in normal circumstances. If a primary does fail, then a new primary is selected from the backups according to the server priority list, as described below.An `alternate’ holds no session data for distributed sessions; it always gets its session data from the primary, and never replicates it. However, if a primary or a backup fails, then an alternate can be selected to be a new backup. If that happens, it will start replicating session data, in case it has to become a primary in the future.A `local’ holds no session data for distribu
