Messaging has rapidly become the one, true business critical application in use today by many, probably most, enterprises. Even more so than Enterprise Resource Planning or other cross-business applications, any failure in the messaging system is noticed by, and affects everyone. If a person cannot get an e-mail to or from another person then they are immediately in contact with the help desk to report the problem. Users are far less inclined to be forgiving when it comes to an e-mail outage; they just expect it to work. As working patterns change, the availability requirements of this mission critical system change with them.

In years past, the mainframe was taken down nightly for batch runs, a situation that is no longer acceptable for today’s messaging platforms. The increase in server power and capabilities is enabling a greater number of users to be hosted on any given server. In many situations, the service availability window is expanding as more time zones require support from a particular server.