Data Guard Broker Tips Oracle Database Tips by Donald BurlesonDecember 9, 2015

Oracle Data Guard - Data Guard Broker

Introduction to Data Guard broker

Data Guard Broker is a tool supplied with Oracle database server software that is designed to ease the processes used in the creation and management of a Data Guard configuration. It is comprised of a server side component known as the DMON process and a client side component known as the CLI or GUI console.  In Chapter 2, "Data Guard Architecture", a brief description on server side and client side components along with the management model was presented.

In this chapter, information will be presented about the broker management model in Oracle10g, which is slightly different from the one in Oracle9i. The main focus of this chapter is to provide practical details on the use of the Data Guard Broker command line interface to create and manage a configuration. It does not present detailed information on using the Data Guard GUI interface, which is integrated with Oracle Enterprise Manager. There are genuine reasons for focusing on CLI interface and not GUI interface. These reasons are:

• GUI interface integrated with OEM provides brilliant online help, so it is very easy to use.
   

• To use GUI interface, Oracle Enterprise Manager 9i Release 2 or later will have to be installed.  This is a separately licensed product and may not be available to all users.
   

• CLI statements can be imbedded in custom scripts and toolkits. Doing so will prove to be very useful at times.

On the disadvantage side, the CLI interface cannot be used to create a physical or logical standby database. They are a prerequisite for using CLI interface of the Data Guard manager.

The difference in the broker management model between Oracle9i and Oracle10g has resulted in significant modifications in the CLI statements between these two releases. Throughout this chapter, wherever applicable, relevant statements from both releases will be provided.

The Data Guard Broker Concept

As described in chapter 2, "Data Guard Architecture", Data Guard Manager (GUI or CLI), DMON process, and site configuration files are the necessary components of Data Guard Broker. Using GUI or CLI interface, commands can be sent to the primary or standby sites, and the DMON process running on the site executes the command on behalf of the Data Guard manager.

In addition to executing the command, the DMON process updates the configuration file if the command modifies any properties or state of the site. Change in the configuration file is communicated to the DMON processes running on other sites, such that a consistent copy of the configuration file can be maintained across the entire Data Guard environment.

The broker management model defines the layers in a Data Guard configuration that can be managed individually through Data Guard broker. The management model varies between Oracle9i and Oracle10g. The management model of Oracle9i has already been presented in chapter 2. The following section presents an overview of the management model in Oracle 10g and beyond (Oracle 11g)

Broker Management Model in Oracle

Oracle10g reduced the complexity of the management model by combining the site and resource layers into one database object layer. As a result, there are only two object layers in the model. These are:

• Configuration Layer - A configuration layer in the management model is a logical grouping of database objects identified by their profile. A profile contains state, status, and properties of the database. There can be one primary and up to nine standby databases in a configuration. The standby databases could be either physical or logical.
   

• Database Object Layer - A database object layer identifies a single database in the configuration.  Each database object has its own exclusive profile.