See Oracle Data Guard Concepts and Administration for the definition of a Data Guard configuration and for complete information about Oracle Data Guard concepts and terminology.
1.1 Overview of Oracle Data Guard and the Broker
Oracle Data Guard ensures high availability, data protection, and disaster recovery for enterprise data. Data Guard provides a comprehensive set of services that create, maintain, manage, and monitor one or more standby databases to enable production Oracle databases to survive disasters and data corruptions. Data Guard maintains these standby databases as transactionally consistent copies of the primary database. If the primary database becomes unavailable because of a planned or an unplanned outage, Data Guard can switch any standby database to the production role, thus minimizing the downtime associated with the outage. Data Guard can be used with traditional backup, recovery, and cluster techniques, as well as the Flashback Database feature to provide a high level of data protection and data availability.
1.1.1 Data Guard Configurations and Broker Configurations
A Data Guard configuration consists of one primary database and up to thirty standby databases. The databases in a Data Guard configuration are connected by Oracle Net and may be dispersed geographically. There are no restrictions on where the databases are located as long as they can communicate with each other. For example, you can have a standby database on the same system as the primary database, along with two standby databases on another system.
The Data Guard broker logically groups these primary and standby databases into a broker configuration that allows the broker to manage and monitor them together as an integrated unit. You can manage a broker configuration using either the Oracle Enterprise Manager graphical user interface or the Data Guard command-line interface.
1.1.2 Oracle Data Guard Broker
The Oracle Data
Guard broker is a distributed management framework that automates and centralizes the creation, maintenance, and monitoring of Data Guard configurations. The following list describes some of the operations the broker automates and simplifies:
Creating Data Guard configurations that incorporate a primary database, a new or existing (physical, logical, or snapshot) standby database, redo transport services, and log apply services, where any of the databases could be Oracle Real Application Clusters (Oracle RAC) databases.
Adding additional new or existing (physical, snapshot, logical, Oracle RAC or non-Oracle RAC) standby databases to an existing Data Guard configuration, for a total of one primary database, and from 1 to 30 standby databases in the same configuration.
Managing an entire Data Guard configuration, including all databases, redo transport services, and log apply services, through a client connection to any database in the configuration.
Managing the protection mode for the broker configuration.
Invoking switchover or failover with a single command to initiate and control complex role changes across all databases in the configuration.
Configuring failover to occur automatically upon loss of the primary database, increasing availability without manual intervention.
Monitoring the status of the entire configuration, capturing diagnostic information, reporting statistics such as the Redo Apply rate and the redo generation rate, and detecting problems quickly with centralized monitoring, testing, and performance tools.
You can perform all management operations locally or remotely through the broker's easy-to-use interfaces: the Data Guard management pages in Oracle Enterprise Manager, which is the broker's graphical user interface (GUI), and the Data Guard command-line interface called DGMGRL.
These interfaces simplify the configuration and management of a Data Guard configuration. Table 1-1 provides a comparison of configuration management using the broker's interfaces and using SQL*Plus.
Table 1-1 Configuration Management With and Without the Broker