"When putting your disaster recovery plan in writing, divide your applications into three tiers," says Robert DiLossi, senior director, Testing & Crisis Management, Sungard Availability Services. "Tier 1 should include the applications you need immediately. These are the mission-critical apps you can't do business without. Tier 2 covers applications you need within eight to 10 hours, even up to 24 hours. They're essential, but you don't need them right away. Tier 3 applications can be comfortably recovered within a few days," he explains.