Introduction to Data Guard Broker

Oracle Data Guard Broker: Introduction

Oracle Data Guard Broker is a distributed management framework. The broker automates and centralize the creation, maintenance an monitoring of data guard configurations. With the broker, you can perform all management operations locally or remotely with easy-to-easy interfaces, like Oracle Enterprise Manager Grid Control and DGMGRL ( a command line interface).

Features:

1. Automated creation of Data Guard configurations incorporating a primary database, a new or existing standby database, redo transport services and log apply services.

2. Adding new or existing standby database to each existing data guard configuration, for a total of one primary database and from one to 30 standby databases in the same configuration.

3. 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.

4. Invoking switchover or failover with a single command to initiate and control complex role changes across all databases in the configuration.

5. Monitoring the status of the entire configuration, capturing diagnostic information, reporting statistics ( such as the log apply rate and the redo generation rate ) and detecting problems quickly with centralized monitoring, testing and performance tools.

Components:

Client-side
         i. OEM Grid Control
        ii. DGMGRL

Server-side
        i. DMON Process
       ii. Configuration File

Configuration:

A Data Guard configuration consists of one primary and up to 30 standby databases. The database in the Data Guard configuration are typically dispersed geographically and are connected by Oracle Net.
                         A Data Guard Broker configuration is logical grouping of the primary and standby databases in a Data Guard configuration. The broker's DMON process configures and maintains the broker configuration components as a unified group of resource objects that you can manage and monitor as a single unit.

Architecture:

The Data Guard Monitor Process (DMON) is an background process that runs on every instance that is managed by the broker. When you start the broker a DMON process is created.

When you use OEM or DGMGRL or DG-CLI( Command Line Interface), the DMON process is the server-side component that interacts with the local instance and DMON processes that are 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 instance has a consistent copy of configuration file in which the DMON process stores its configuration data. There are two multiplexed versions of the configuration file on each instance.

DMON (Data Guard Monitor) Process:

The DMON Process is an Oracle background process that is part of each database instance managed by the broker. When you start the Data Guard broker, a portion of SGA is allocated and a DMON process is created. The amount of memory allocated is typically less than 50KB per site.

When you use OEM or DGMGRL or DG-CLI( Command Line Interface), the DMON process is the server-side component that interacts with the local instance and DMON processes that are 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 instance has a consistent copy of configuration file in which the DMON process stores its configuration data. There are two multiplexed versions of the configuration file on each instance.

The DIAGNOSTIC_DEST parameter defines the location for diagnostic files such as trace files and core files. The structure of the directory specified by DIAGNOSTIC_DEST is as follows:

<DIAGNOSTIC_DEST>/diag/rdbms///

This location is known as the Automatic Diagnostic Repository (ADR) Home. The DMON trace files are located in the /trace sub-directory.

Benefits:

>> Enhances the high availability, data protection, and disaster protection capabilities inherent in Oracle Data Guard by automating both configuration and monitoring tasks.

>> Streamlines the process for any one of the standby databases to replace the primary database and take over the production processing.

>> Enables easy configuration of additional standby databases.

>> Provides simplified, centralized and extended management.

>> Automatically communicates between the databases in a Data Guard Configuration by using Oracle Net Services.

>> Provides build in validation that monitors the health of all databases in the configuration.