Maximum Tolerable Outage Alphabet Soup

Specialist subjects are notorious for their abundance of acronyms and BCM with its “maximum tolerable outage” or MTO for systems is no exception. How many members of the MTO family are there? At the last count there were seven, although families often grow, especially when you’re not looking. Here’s the list: Maximum Acceptable Downtime (MAD), Maximum Acceptable Outage (MAO), Maximum Allowable Outage (MAO), Maximum Tolerable Downtime (MTD), Maximum Tolerable Outage (MTO), Maximum Tolerable Period of Disruption (MTPD) and Time To Live (TTL). They all mean the same thing and encompass the same two measures for getting business functioning again after interruption. Any guesses?

First, a quick reminder about defining maximum tolerable outage: it’s the maximum amount of time an organisation can tolerate a business process being unavailable before suffering serious, negative consequences. MTO can then be divided into two parts. The first part is the RTO or the Recovery Time Objective. This is the maximum time for systems to be brought back to a “normal” functioning state (where “normal” is defined between interested parties in the organisation). The second part is Work Recovery, the time needed to recover lost transactions and to absorb the backlog of work created due to the outage.

Apart from the basic equation of “maximum tolerable outage = RTO + work recovery”, there are two further concepts that accompany MTO when applied to IT systems: one comes before MTO (thinking about this as a timeline) and the other one after. The one that comes before is RPO, or Recovery Point Objective: this refers to how out of date you can afford your data to be when your systems are once again operational, which in turn determines your frequency of data backups. The one that comes after is Restoration Time, the time needed to get back to full business continuity by backing up the recovered system and making any necessary adjustments to BCM.