The goal of any disaster recovery plan is to ensure the survival of the business when an IT facility becomes unavailable for an extended period. The immediate objective is to restore service at a remote location when the local (normal) computing facility is no longer available.

What’s a remote location and how remote is remote enough? In case of a fire in your building, a location a few hundred yards away may be sufficient. However, if the disaster is a hurricane, the facility may need to be several states away. In general, the farther away the better.


Business needs typically dictate the disaster recovery methods chosen. The more data and service availability a method provides, the more costly it will be.

Imagine you’re handling IMS disaster recovery planning for your organization. Management tells you that no data or only a small percentage of data can be lost, and that services can’t be down for more than a few minutes.

When you evaluate a disaster recovery method that can ensure these goals are met, you find that the cost is extremely high. In short, cost goes up as data loss and service unavailability go down. Management then begins to reconsider: “At that high cost, perhaps we can afford to lose a little more data after all. Perhaps services can be unavailable for a little longer than we first thought.”

Top management needs to answer these questions:

  • What disaster are you most worried about and how large a geographic area would it affect? An explosion at a chemical plant could affect an entire city. An earthquake could affect a large part of a state.
  • How much data can your organization lose? Is the answer “zero” or is it acceptable to recover data from a set point in time?
  • How long can your organization go without IMS service? Your disaster recovery plan needs to spell out the length of time it would take to restore service. Data loss and service availability aren’t the same. For one organization, zero loss of data may be required, but IMS service can be down for a day. For another organization, survival might mean being back in service in an hour, even if the trade-off is to lose an entire day’s worth of data. It all depends on the business you’re in.
  • How much can you spend? When senior management learns the expense involved in achieving their disaster recovery goals, they may change their goals. In effect, disaster recovery planning is an iterative process. Management will probably evaluate several proposals before arriving at a solution that best balances the needs of the business with the cost of the plan.
  • How much downtime is tolerable? It may be OK to periodically terminate all your IMS systems to establish your disaster recovery points. Or, more commonly, your systems and databases may need to be continuously available and establishing a disaster recovery point can’t impact system and data availability.

The closer you get to zero data loss with no downtime and no impact on system and data availability at the local IT center, the greater the cost of the disaster recovery method.


Disaster recovery methods or solutions can be grouped into three main categories: hardware solutions, special-purpose software solutions, and manual solutions. These solutions or processes aren’t mutually exclusive and there are as many combinations as there are IT environments.

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