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Oracle9i Data Guard Broker Concepts

This chapter describes the Oracle9i Data Guard broker, its architecture and components, and how it automates and simplifies the creation, control, and monitoring of a Data Guard configuration.

The following sections introduce Data Guard broker terminology and concepts:

• Section 1.1, "Oracle9i Data Guard Broker Overview"

• Section 1.2, "Data Guard Broker Management Model"

• Section 1.3, "Data Guard Broker Architecture and Components"

• Section 1.4, "Benefits of the Data Guard Broker"

• Section 1.5, "Oracle9i Data Guard Prerequisites"

  
  

  See Also: Oracle9i Data Guard Concepts and Administration for complete information about Oracle9i Data Guard concepts and terminology.

1.1 Oracle9i Data Guard Broker Overview

The Oracle9i Data Guard broker is a distributed management framework that automates and simplifies most of the complex operations required to create, control, and monitor a Data Guard configuration.

The following list provides examples of some of the operations that the broker automates and simplifies:

• Creation of local and remote standby databases

• Configuration, control, and monitoring of log transport services

• Configuration, control, and monitoring of log apply services

You can perform all of these operations locally or remotely, using Oracle9i Data Guard Manager, which is the broker's graphical user interface (GUI). With the Data Guard command-line interface (CLI), you can perform all of these operations except for the creation of standby databases.

The creation of local or remote standby databases, which is a very complex operation, is greatly simplified through a wizard that is part of Data Guard Manager. The wizard:

• Automates the creation of the standby control file, the standby initialization parameter file, and the standby datafiles

• Makes all Oracle Net configuration changes necessary to support log transport services

The broker allows you to quickly and easily verify that log transport services and log apply services are configured and functioning properly. For example, the broker allows you to easily view information such as the number of logs ready to be shipped from the primary site, the number of logs to be applied on the standby site, and other data specific to the standby database.

The ability to monitor local and remote databases and to respond to events is also significantly enhanced by the broker through its health check mechanism and its interaction with the Oracle Enterprise Manager event management system.

See Also: Oracle9i Data Guard Concepts and Administration for a complete description of the discrete steps that comprise the creation of a standby database and the other monitoring and control operations that have been automated or simplified by the broker.

1.2 Data Guard Broker Management Model

The broker simplifies the management of a Data Guard environment by performing operations against three logical objects:

• Configuration

• Site

• Database resource

These objects represent the physical configuration, site, and database entities in the actual Data Guard configuration.

The broker currently supports Data Guard configurations that contain one primary and one standby database. A supported broker configuration therefore consists of one configuration object, which contains two site objects. One of these site objects will contain a database resource object that represents a primary database and the other will contain a database resource object that represents a standby database.

Figure 1-1 shows the hierarchy of these objects.

Figure 1-1 Hierarchy of Objects Managed by the Data Guard Broker

Text description of the illustration mgtmodel.gif

A configuration object is at the highest level in the hierarchy of objects managed by the broker. A configuration object is a named collection of sites and the resource objects that those sites contain.

A site object is at the middle level in the hierarchy of objects managed by the broker. A site object is a named collection of resource objects that reside on a single host. The broker currently supports one type of resource object, and that is the database resource object.

A database resource object is at the lowest level in the hierarchy of objects managed by the broker. It is a named object that corresponds to a primary or standby database instance. The broker uses this object to manage and control the state of a single database.

Because these objects are connected in a hierarchy, you can perform complex operations on a single object or on all objects in an entire configuration with a single mouse click or command. For example, you can bring each database resource and site in a configuration online one at a time, or bring them all online at the same time in a single step by bringing the configuration itself online.

See also: Chapter 2 for more information about how to control an object through its states and properties

1.3 Data Guard Broker Architecture and Components

The Oracle9i Data Guard broker provides the following components:

• Oracle9i Data Guard Manager

• Data Guard Command-Line Interface (DGMGRL)

• Data Guard Monitor

Figure 1-2 shows the components of the broker.

Figure 1-2 Components of Oracle9i Data Guard Broker

Text description of the illustration odg.gif

1.3.1 Data Guard Broker User Interfaces

You can use either of the broker's user interfaces to create a broker configuration, and to control and monitor the configuration from any host in the configuration. The broker provides two user interfaces:

• Oracle9i Data Guard Manager

• Data Guard Command-Line Interface (DGMGRL)

1.3.1.1 Oracle9i Data Guard Manager

The Data Guard Manager is a graphical user interface that works with the broker and Oracle Enterprise Manager to automate and simplify the management of a Data Guard configuration. Because it is integrated with Oracle Enterprise Manager, Data Guard Manager allows you to manage your configuration using a familiar interface and event management system.

Data Guard Manager includes:

• Wizard-driven creation of local and remote standby databases.

• Wizard-driven import of existing primary and standby databases into a broker configuration.

• Complete monitoring and proactive event reporting through e-mail or pagers.

Figure 1-3 shows the general page from the Oracle9i Data Guard Manager console.

Figure 1-3 Oracle9i Data Guard Manager Console

Text description of the illustration guiconfg.gif

See Also: The Oracle9i Data Guard Manager online help and quick tour

1.3.1.2 Data Guard Command-Line Interface (DGMGRL)

The Data Guard command-line interface (CLI) allows you to control and monitor a Data Guard configuration from the CLI prompt or within scripts. You can perform most of the activities required to manage and monitor the objects in the configuration using the CLI.

The following example lists the available commands:

DGMGRL> HELP
The following commands are available:
quit
exit
show                See "help show" for syntax
enable              See "help enable" for syntax
disable             See "help disable" for syntax
help                 [<command>]
connect             <user>/<password> [@<connect>]
alter               See "help alter" for syntax
create              See "help create" for syntax
remove              See "help remove" for syntax
shutdown
startup

This manual provides examples and reference information for the Data Guard command-line interface.

See Also: Chapter 6 for complete reference information for the Data Guard command-line interface

1.3.2 Data Guard Monitor

The configuration, control, and monitoring functions of the broker are implemented by server-side software and configuration files that are maintained on each site that the broker manages. The software is called the Data Guard monitor.

The following sections describe how the Data Guard monitor interacts with the Oracle server and with remote Data Guard monitors to manage the sites in a broker configuration.

1.3.2.1 Data Guard Monitor (DMON) Process

The Data Guard monitor process (DMON) is an Oracle background process that runs on every site that is managed by the broker. When you start the Data Guard monitor, a portion of the system global area (SGA) is allocated and a DMON process is created.

When you use Data Guard Manager or the CLI to manage an object, the DMON process is the server-side component that interacts with the local instance and the DMON processes running on other sites to perform the requested function. The DMON process is also responsible for monitoring the health of the broker configuration and for ensuring that every site has a consistent copy of the binary configuration files in which the DMON process stores its configuration data.

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See Also: Oracle9i Database Concepts for more information about the memory structures and processes that are used to implement an Oracle database instance

Figure 1-4 shows the DMON process among the several background processes that perform maintenance work for the Oracle database server.

Figure 1-4 Oracle9i Broker Background Process

Text description of the illustration dmon.gif

The zigzag arrow in the center of Figure 1-4 represents the two-way Oracle Net communication channel that exists between the DMON processes on sites in the same broker configuration.

This two-way communication channel is used to pass requests between sites, and to monitor the health of all of the sites in the broker configuration.

1.3.2.2 Configuration Management

The DMON process maintains persistent configuration data in a binary configuration file on each enabled site in the broker configuration. This data is managed transparently by the DMON process to ensure that the configuration information is kept consistent across all of the sites.

The broker uses the data in the configuration file to configure and start the site and resource objects.

1.4 Benefits of the Data Guard Broker

Through the broker's easy-to-use interfaces, you can automate the tasks required to configure and control sites and database resources in a broker configuration. The broker provides an efficient and effective solution for managing a configuration, with the following benefits:

Enhanced high availability and disaster protection.	The broker automates the tasks required to configure and monitor a primary and standby database configuration. The broker's easy-to-use interfaces enhance the high availability and disaster protection capabilities that are inherent in an Oracle9i Data Guard configuration.
Centralized, uniform management interface.	The broker allows DBAs to choose from two different interfaces to configure databases into a single logical configuration: Oracle9i Data Guard Manager graphical user interface or the Data Guard command-line interface.
Automated creation and configuration of physical standby databases.	Data Guard Manager provides a wizard that automatically creates and configures the standby database, including creation of the standby control file, initialization parameter file, and the standby datafiles. Although the CLI interface cannot automatically create a new standby database, the CLI can configure and monitor an existing standby database.
Automated configuration of log transport services and log apply services.	The broker allows you to monitor and control all of the aspects of the Data Guard configuration, including the primary and standby databases, log transport services, and log apply services. The standby site accepts redo logs shipped from the primary site and log apply services apply changes to the standby copy of the database.
Simplified and extended management.	You can coordinate resource state transitions and modify resource properties while ensuring that changes are made to all of the sites in the configuration.
Protection through built-in monitoring and alert and control mechanisms to detect problems.	The broker provides built-in validation that monitors the health of all of the sites in the configuration. You can update parameters for the Data Guard environment, and monitor and control all critical resources from a centralized point.
Unattended operation.	To accomplish unattended operation so that processing can continue without human intervention, the DBA can use scripting through the CLI or by implementing events using Data Guard Manager.
Distributed monitoring and alert and control mechanisms from a single system.	The broker automates and centralizes the management and operational tasks a DBA must perform across multiple sites in a Data Guard configuration. The broker monitors the status of the entire configuration, including all of the sites and resources in the Data Guard configuration
Dynamic altering of properties and states.	In addition to adding and removing sites and resources, you can change properties and operational states of objects in the configuration without incurring any downtime.

1.5 Oracle9i Data Guard Prerequisites

Oracle9i Data Guard is installed automatically when you install the Oracle9i Enterprise Edition database server. You must install the Oracle9i Enterprise Edition database server on each site where you plan to manage broker configurations.

You must install Oracle9i Data Guard Manager separately. It is installed with the Oracle Enterprise Manager software.

The following conditions must be true before you can use the broker:

• The primary and standby databases must be running Oracle9i and installed in a single-instance environment (not an Oracle Real Applications Clusters environment). The database server must be licensed for Oracle9i Enterprise Edition.

• The value of the DRS_START parameter must be TRUE. See Section 2.2 for more information.

• Oracle Net network files must be set up on the primary database site and on the the standby database site if you configure an existing standby database into the broker configuration. Otherwise, Data Guard Manager automatically sets up the network files when it creates a standby database.

• The primary instance must be opened in archivelog mode. If there is an existing standby instance, it must be mounted.

• If you plan to configure an existing standby database into the broker configuration, you must set up a remote login password file to enable management of a remote standby database. Otherwise, Data Guard Manager automatically sets up the remote password file when it creates a standby database.

  See Also: Section 2.2 for more information about preparing and starting Oracle9i Data Guard. See Oracle9i Data Guard Concepts and Administration for more information about setting up the network files.