DR drill
Also called: disaster recovery drill, failover test, game day
A DR drill is a deliberate rehearsal of your disaster-recovery procedure, typically a planned switchover or a restore-and-promote in the DR region, run while everything is healthy, to prove the plan works and to measure your real RPO and RTO.
What this means
A rehearsal of your disaster plan while everything is still healthy, usually a planned switchover, or a restore-and-promote in the backup region. You run it to prove the plan actually works and to measure your real recovery point and recovery time, before a genuine outage tests them for you.
Why it matters operationally
An untested DR plan has an unknown RTO. Drills surface the gaps that only appear under a real role change, stale connection strings, missing roles, slow detection, before an actual disaster forces you to discover them the hard way.