Interaction Between the Data Guard Broker and a Data Guard Configuration [ID 249703.1]

Interaction Between the Data Guard Broker and a Data Guard Configuration [ID 249703.1]
	Modified20-OCT-2010TypeFAQStatusPUBLISHED

PURPOSE

-------

This bulletin will show details about DataGuard, what it is and how it makes it

easier to manage your Standby databases. It also shows the interaction between

the DataGuard configuration and the database.

SCOPE & APPLICATION

-------------------

Intented to be used for administrators managing or planning to implement a

Data Guard (Broker) environment.

1. Data Guard Broker and Standby Database

-----------------------------------------

Basically, it is possible to create/run a Physical/Logical standby database

without the Data Guard Broker (see notes in "Related Documents"). The Data Guard

Broker itself is an offset to the Standby database making maintainance and

administration of several Standby databases much easier. Data Guard Broker uses

an own process (DMON) on each Primary/Standby database and own configuration

files for interaction.

The process is started if you set the initialization parameter

'DG_BROKER_START' to TRUE. To create and maintain the configuration files, you

need to create a Data Guard configuration either using the Data Guard wizard

from Enterprise Manager Grid Control, resp. the DataGuard Manager or you do this

manually using the command line DGMGRL. Both procedures are also shown in Notes

refered in "Related Documents".

2. The DataGuard Configuration

------------------------------

Once you created a Data Guard Broker configuration using one of the ways

mentioned above, you have a basic Data Guard Broker configuration running.

This configuration has its own parameters and settings. They are maintained in

the DataGuard metadata configuration files. There exist two configuration files

on each Site. These files must also be accessible from the database, therefore,

the initialization parameter 'DG_BROKER_CONFIG_FILEn' points to the corresponding

configuration files. These files and all related settings are only altered or

maintained if the configuration is created and enabled. DO NOT edit these

files manually. They are binary files, editing them with an editor can destroy

these files and your DataGuard configuration !!

If the database (Primary and/or Standby database) is a RAC database (10.1.0+),

then all instances have to use the same Data Guard Broker configuration files,

ie. they have to reside on the shared disk (RAW devices, CFS or ASM).

3. The Control of DataGuard

---------------------------

The Data Guard Broker configuration can either be administered via the Data

Guard Manager GUI as part of the Enterprise Manager (Grid Control) or via the

Data Guard Manager command line DGMGRL. All are cooperating with each other and

make sure the Data Guard Broker configuration information is consistant. So

they all revert to the same configuration files as mentioned before. So all

changes you make on the Data Guard Manager impacting the configuration files

and the database resp. its parameters. The advantage you have here is that you

do not have take care of the database parameters and status, Data Guard Broker

does this for you and you can administer the Primary and Standby database either

using the GUI or some simple commands in the command line interface. The changes/

commands you run on the DataGuard Manager are executed on either the Primary or

Standby or both, depending on the command. There's no separate connection from

you to the databases required and Data Guard Broker decides which databases are

related to your command.

4. Interaction between Data Guard Broker and the Primary/Standby Database

--------------------------------------------------------------------------

By setting the initialization parameter 'DG_BROKER_START' to TRUE, the

Data Guard Broker Managing Process (DMON) is started. This process must be

started on all databases (Primary and Standby) involved in the configuration.

The DMON process reads the configuration files on its site and sets the

required database parameter accordingly, eg. in the Data Guard Manager you set

the parameter 'STANDBY_ARCHIVE_DEST' to a certain value. This value will be

written into the corresponding DataGuard configuration file. The DMON sees this

information and updates the database parameters accordingly. A prerequisite for

this functionality to run correctly is the usage of a Server-parameterfile

(SPFILE), of course.

5. Troubleshooting

------------------

Most problems come from a wrong Data Guard configuration or misplaced settings

in the Data Guard configuration files. If any problem occurs you first

of all should sort out if this is a Data Guard Broker or Standby database

problem. So you can either try to disable your configuration or set

'DG_BROKER_START' to FALSE and verify your Standby database still works

correctly. If this is not the case, it seems to be a Standby database issue, so

see the ALERT.LOG-files from Primary and Standby database for more Hints. If

your Standby database still works well it is most likely you have a problem

with Data Guard Broker. Many hints mostly can be found in the DRC<SID>.LOG-file,

which is written by the DMON. This file can be found in the same directory

where the ALERT.LOG is located on each instance part of the configuration.

Wrong settings and communication problems are mostly logged there.

RELATED DOCUMENTS

-----------------

Data Guard, Concepts and Administration

Data Guard Broker

Note:180031.1: Creating a Data Guard configuration

Note:186150.1: Data Guard 9iCreating a Logical Standby database

Note:214071.1: Creating a configuration using Data Guard Manager

Note:201669.1: Setup and maintenance of Data Guard Broker using DGMGRL

Note:745201.1: Diagnosing Connection Problems with an active Data Guard Broker configuration

Related

---

------------------------------------------------------------------------------