Storage

Imagine a haggard CIO being interviewed about a recent failure in his production applications. You might hear this lament:  

“Last year, I spent millions of dollars on a storage replication solution to protect my data in case of a disaster. Yesterday, my business lost millions of dollars due to some improper database system maintenance. The recovery action took hours to diagnose and prepare, and even longer to execute. We’ll probably lose several accounts permanently and will never be able to recoup the losses. The storage replication solution offered no protection from the outage. I wish I had some tools that could reduce or eliminate the downtime for ‘local’ outages as well as protect for disaster situations.”

Companies have invested millions of dollars in their mainframe database applications. These applications allow trains and planes to move, shipped packages to be tracked, financial transactions to execute, and manufacturing to proceed. If these applications are unavailable for any reason, the company isn’t receiving the expected gain on its investment. Further, some industries incur fines if certain transactions aren’t processed in a timely fashion. Recent legislation requires all publicly traded institutions to maintain a high-availability application plan, including recovery from total site disaster.  

On Aug. 14, 2003, the Northeastern U.S. experienced a massive power blackout. Independent surveys taken since then indicate that more than two-thirds of all respondents lost at least one full business day due to the blackout. The cost of the downtime ranged from $50,000 to more than $1 million per hour.  

The challenge facing a mainframe database application user is to maintain the recoverability of the database while not adversely impacting availability. There are several techniques to protect the database and ensure recovery to a consistent point. The techniques range from periodic dumps of storage onto transportable media, to synchronous I/O mirroring at a second site.

Most companies have at least a basic Disaster Recovery (DR) plan for mainframe database applications. In recent years, companies have begun to address the larger issue of business continuity, recognizing that ensuring application availability requires more than just a DR plan.  

This enlargement of scope presents challenges and opportunities for companies to consider. Many companies combine a variety of solutions to completely protect the strategic database asset. Recovery solutions may include both hardware and software technologies, which provide different protection for different exposures.  

The Hardware Solutions

Hardware solutions may be driven by disk storage technology or by host-based processor systems. Generally, the hardware replication solutions take two forms: point-in-time backups and remote replication.  

Point-in-time backups are based on creating a consistent local copy of data, and making the copy available at a remote site. This occurs via either dumping to tape and shipping the tapes to a vault, or electronically transmitting the backup data set(s) to a remote set of volumes. Depending on the vendor technology used, these backups may be full-volume or data set-level operations, and may create a complete copy of the data or merely generate additional directory pointers to data. Typical data loss in this scenario is 24 hours (although if additional log data is available, it may be applied to a point-in-time backup to lessen the data loss). An application outage is usually required to ensure data consistency for a point-in-time backup. Some examples of this technology include:  

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