Continuous Availability Services
By David Nolan
Business Continuity is the underlying objective of all Contingency Plans; however, the requirements for Business Continuity vary by
application within an organization, as well as from company to company.
Solutions employing electronic technology range from immediate synchronized recovery of most critical applications to recovery of less critical applications in days or weeks. In all cases, data integrity is the first and foremost concern.
It has long been recognized that recovery begins with corporate data. For most organizations, the vital records program has three key components:
Off-site tapes provide a basis for recovery to some prior point in time by providing access to Archive and Operational data. On-site transaction Journals or Logs provide protection in the event of system or disk failure at the primary processing site. Neither, however, provides for the protection of daily transactions in the event of a serious facility outage.
CONTINUOUS AVAILABILITY SERVICES
Solutions are being implemented today which employ communications and systems technology to provide data integrity and reduced recovery time.
ELECTRONIC VAULTING, the bulk transfer of backup data over communications facilities, can simplify the backup process and provide more timely offsite Operational data protection. This process can be facilitated with a host-to-host or channel extension connection and typically serves to reduce, but not eliminate the exposure to loss of data.
REMOTE JOURNALING delivers realtime data integrity by capturing and transmitting the Journal and Transaction Log data offsite as it is created. This solution utilizes a software product known as ENET1,which interacts with standard database journal and logging facilities in IMS, CICS, IDMS, CPCS and other DBMSs. Just prior to the writing of the Journal, ENET, utilizing a user exit and Cross Memory Services, copies the Journal record into its own address space and immediately lets the Journal write continue. ENET then transmits the Journal data offsite using SNA as a standard VTAM Application. This technique requires a host-to-host communications link.
In addition to being the only realtime data protection product available today, Remote Journaling provides the basis for the use of In-place Forward Recovery procedures for recovery of Database Shadowing. Additionally, there are no application changes and minimal communications requirements involved with the use of this technology.
Used in conjunction with traditional alternate site recovery programs, Remote Journaling enables a customer to validate the complete recovery process including Transaction data recovery without disrupting the user community.
AN INTEGRATED SOLUTION
For some companies, data integrity is only the tip of the iceberg. Their requirements include recovery of most critical applications in hours or even minutes. Even so, these applications represent a relatively small percentage of the total recovery requirement.
An integrated solution is required to maintain price/performance of the recovery program and adds to the equation:
DATABASE SHADOWING, which reduces recovery time by staging the database restore and roll-forward process, enabling recovery within hours.
STANDBY SERVICES, which provide recovery of most critical applications in a matter of minutes and GUARANTEED access to an alternate processor.
There are two key elements in all cases: all of the Operational and Transaction data is available, and the solutions are integrated into the hot site recovery capability. The Continuous Availability Services enhance and refine the typical disaster recovery process by adding flexibility, data integrity and reduced recovery time to subscribers.
As the business world advances the use of technology for competitive advantage, traditional disaster recovery programs will have to evolve to keep pace. While faster recovery times and automated off-site backup are tempting targets for disaster recovery program enhancements, backup of transaction data represents the biggest exposure for most companies.
David Nolan is the Assistant Vice President of Marketing and Sales at Comdisco Computing Services Corporation.
This article adapted from Vol. 3 No. 3, p. 19.
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