Configure a hidden / non-voting member

Command

cfg = rs.conf(); cfg.members[2].hidden = true; cfg.members[2].priority = 0; cfg.members[2].votes = 0; rs.reconfig(cfg)

What it does

Makes a member hidden (invisible to the application), non-voting and priority 0, using it only for backup/analytics.

When to use it

When you want to isolate backups or analytical queries.

Caution

A hidden member must have priority 0; otherwise reconfig fails.