In today’s market conditions, business continuity and disaster recovery are a top priority for senior management of most global enterprises. A global enterprise has to deal with economic fluctuations, rapid changes in market trends and competitive pressures on a 24x7 basis, and must be able to swiftly and efficiently deal with unforeseen business interruptions.

VESL Technologies with global experience of more than 15 years in the implementation of Oracle Technologies offer Oracle Active Data Guard as the most effective solution available today to provide Business Continuity and Disaster Recovery by protecting the core asset of any enterprise – its data, and make it available on a 24x7 basis even in the face of disasters and other calamities. This document describes Oracle Active Data Guard technology, demonstrates a brief on what has been implemented, and how it is one of the most important elements in the business continuity infrastructure of any enterprise.


With the proliferation of E-Business and Corporate Governance, an enterprise today operates in an extremely complex and a highly networked, global economy, and is more susceptible to interruptions than in the past. The cost of such interruptions, or downtimes, varies across industries and can be as much as millions of dollars. While that number is staggering, the reasons are quite obvious. The Internet has brought millions of customers directly to the electronic storefronts. Critical and interdependent business issues such as customer relationships, competitive advantages, legal obligations, industry reputation and shareholder confidence are even more critical now because of their increased vulnerability to business disruptions and downtimes.


disaster_1.jpgDowntime that affects a business could be either unplanned or planned. Unplanned downtimes may be caused by hardware or system failures, data/storage failures, human errors, computer viruses, software glitches, natural disasters and malicious acts. A business may also have to undergo planned downtimes because of scheduled maintenances such as system upgrades.

A company designing its business continuity strategy must create a Business Continuity Plan (BCP) that can effectively deal with each of these challenges. One of the underlying foundations of such a BCP is that it must offer protection of company data, since data is one of the most critical company assets – whether it is payroll/employee information, customer records, valuable research, financial records, historical operations information, etc. If a company loses its data, it cannot be replaced, and rebuilding/regenerating that data will likely be an extremely expensive, if not an impossible task, critically impacting the company’s ability to stay in business.

disaster_3.jpgFailover to a Standby Database

The switchover option, on the other hand, is the planned role reversal of the primary and standby databases, to handle planned maintenance on the primary database. The main difference between a switchover operation and a failover operation is that switchover is performed when the primary database is still available, and it does not require re-instantiation of the database. This allows the primary database to assume the role of a standby database almost immediately. As a result, scheduled maintenance can be performed more easily and frequently. For example, switchover may be used to perform an upgrade on the primary site by switching over all of the database clients to the standby site as hardware is upgraded on the primary site.

Both failover and switchover operations guarantee zero data loss if Data Guard was being run in the maximum protection mode or maximum availability mode at the time of the failover or switchover.Failover and switchover operations also work seamlessly when multiple standby databases are included in the configuration. For example, if multiple standby databases are configured and the primary database goes down, the administrator has the flexibility to choose one of the available standbys to become the primary. Data Guard fully automates the process of redirecting the other standby databases to use the new primary, including shipping any missing or incomplete redo data.