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Executive Overview

A critical objective for any enterprise is the protection of corporate assets, including data. 

Enterprises are equally concerned about the impact of application downtime when databases 

become unavailable due to outages caused by data corruptions, component, system and site 

failure, or human error. Increased cost, lost revenue, negative publicity, and regulatory non￾compliance are just a few of the many negative consequences resulting from data loss and

downtime. 

Even though a bullet-proof disaster recovery (DR) solution offers the ultimate protection for 

enterprise data, businesses often don’t place a high priority on DR due to the fact that disaster 

recovery infrastructure is expensive and rarely used. This leads to under-investment in DR

and/or the deployment of solutions that provide inadequate protection and little assurance that 

they will actually work when called upon. 

Oracle Data Guard and Active Data Guard fundamentally changes what enterprises should 

expect from a DR solution for the Oracle Database. It provides the best possible data 

protection and application availability and simultaneously reduces the cost of DR by utilizing 

standby systems to offload production workload while in a standby role. Data Guard’s deep 

integration with Oracle Database also enables automatic failover for unplanned outages and 

database rolling upgrades to minimize downtime and risk when performing planned 

maintenance. These capabilities make Data Guard a comprehensive solution for HA and DR.

Active Data Guard also eliminates the risk inherent in generic data protection offered by 

storage-centric solutions such as array-based remote mirroring. Only Active Data Guard 

provides continuous real-time application level validation that the DR system is ready for 

failover if needed. 

This brief is intended for I.T. Managers and Architects who are evaluating disaster recovery 

solutions for the Oracle Database and describes why Data Guard and Active Data Guard are

preferred to traditional DR solutions based on storage technologies. 

Oracle Active Data Guard vs. Storage Remote Mirroring

Introduction: Data Guard and Active Data Guard 

Managed Standby, the precursor to Data Guard, first appeared in Oracle 7. It offered very basic 

archive log shipping capabilities that required complementary scripts to maintain a synchronized replica 

of a production database at a remote destination for DR. Data Guard was introduced as an included

feature of the Oracle Database with Oracle 9i. It represented a major evolution in technology, 

eliminating the need for external scripts and providing complete management, monitoring, and 

automation software to create and maintain one or more replicas (standby databases) of the production 

database (primary). 

Standby databases protect Oracle data from data corruptions, system and software failures, human 

error and disasters. Production applications can quickly switch to the standby database if the primary 

becomes unavailable for any reason. Data Guard with Oracle Database 10g added significant high 

availability (HA) features, making it a comprehensive solution for HA/DR optimized for the Oracle 

Database. 

Active Data Guard was introduced with Oracle Database 11g Release 1 to provide important 

extensions to basic Data Guard functionality that further enhance data protection, availability, and 

return on investment (ROI) in standby systems. Active Data Guard is a separately priced database

option that inherits all Data Guard capabilities while adding numerous advanced features.1 The 

introduction of Oracle Multitenant Architecture in Oracle Database 12c extends all of Active Data 

Guard’s benefits to consolidated database environments whether on premises or in the Cloud. Active 

Data Guard’s many use-cases are described in Figure 1.

Figure 1: Data Guard and Active Data Guard Use Cases

1 www.oracle.com/goto/dataguard

2

Oracle Active Data Guard vs. Storage Remote Mirroring

Why Data Guard Provides the Best Data Protection 

Before Data Guard was introduced, storage based remote mirroring (array mirroring) was the most 

prevalent method of providing real-time protection for the Oracle Database. Array mirroring is a 

sophisticated technology promoted as a generic infrastructure solution that makes a simple promise –

whatever is written to a primary volume will also be written to a mirrored volume at a remote site. 

Keeping this promise, however, can have disastrous consequences for data protection and availability 

when the data written to primary volumes is corrupt.

Data Guard and Active Data Guard are designed to provide greater data protection and availability 

than is possible using storage technologies alone. Many enterprises have been replacing array mirroring 

with Active Data Guard for their business critical databases for the following reasons:

Superior Isolation, Bandwidth Efficient

Simply stated, it is architecturally impossible for generic infrastructure solutions based upon array 

mirroring to provide the same level of data protection as Data Guard. Data Guard is a light-weight 

Oracle-aware solution that provides superior isolation between the production database (the primary)

and its standby database(s). Isolation from faults that can impact the primary copy is the most critical 

aspect of data protection. A high level description of Data Guard architecture is provided in Figure 2. 

Data Guard replicates only the information needed to recover an Oracle transaction (redo) which 

represents a small percentage of the total write volume generated by an Oracle database. Data Guard 

replicates data directly from the memory of the primary database ensuring that the standby is isolated

from corruptions that can be introduced by the I/O stack.