Oracle Data Guard by Nagaraj Ramamurthy_97

8/3/2019 Oracle Data Guard by Nagaraj Ramamurthy_97

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WHAT IS DATA GUARD

Oracles disaster recovery solution for Oracle data;

Feature of Oracle Database Enterprise Edition (EE);

Automates the creation and maintenance of one or moretransactionally consistent copies (standby) of the production

(or primary) database;

If the primary database becomes unavailable (disasters,

maintenance), a standby database can be activated and

assume the primary role.


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SIMPLY PUT

Data Guard helps you protect your Data.

Takes your data and automatically puts it elsewhere

Makes it available for Failover in case of failure.

The other capabilities are.

Switchover for Maintenance

Reporting Off-loading Queries

Backups


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ARCHITECTURE

Oracle

Net

FALPrimary

Database

Transactions

Physical/Logi

calStandby

Database

Backu

p /

Reports

LGWR

Online Redo

Logs

Archived Redo

Logs

ARCH

RFS

Standby

Redo

Logs

Archived RedoLogs

ARCH

MRP/ LSP


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ARCHITECTURE CONTINUES

Primary Database:

A Data Guard configuration contains one production database, alsoreferred to as the primary database that functions in the primary role.

The primary database can be either a single-instance Oracle databaseor an Oracle Real Application Clusters database.

LGWR / ARCH Process

Collects Redo data from Primary and ship that to Standby .

Fetch Archive Log (FAL) Process

Provides client-server mechanism for shipping archived logs to theStandby.

For automatic gap resolution and resynchronization.


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Standby Database:

A standby database is a transactionally consistent copy of the primary database.

Data Guard automatically maintains each standby database by transmitting redo data from the primary database and thenapplying the redo to the standby database.

Physical standby database

Physical Standby

Technology introduced in Oracle 7.2Marketed as Data Guard in Oracle 8.1.7 and above

Standby is identical copy of primary database

Redo changes

transported from primary to standby

applied on standby (Redo Apply)

Can switch operations to standby

Failover time deplaned (switchover / switchback)

Unplanned (failover)

pendent on various factors

Rate of redo generation / size of redo logs

Redo transport / apply configuration


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Logical standby database

Introduced in Oracle 9.2

Subset of database objects

Redo copied from primary to standby

Changes converted into logical change records (LCR)

Logical change records applied on standby (SQL Apply)

Standby database can be opened for updates

Can modify propagated objects

Can create new indexes for propagated objects

May need larger system for logical standby

LCR apply can be less efficient than redo apply

Array updates on primary become single row updates on

standby


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Processes Involved in Standby Recovery phase:

Remote File Server (RFS)

Receives Redo records from the Primary Database.

Managed Recovery Process (MRP)

Apply Redo information to the Physical Standby.

Logical Standby Process (LSP)

Apply SQL translated Redo information to the Logical standby.


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MEDIARECOVERY PROCESS (MRP) -

REDOAPPLY


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LOGICAL STANDBY PROCESS (LSP) -

SQL APPLY


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SQL Apply uses a collection of parallel execution servers and

background processes.

Reader process Reads redo records from the archived logs;

Preparer process Covert the block changes into table changes,Logical Change Records (LCRs);

Builder Process Assembles completed transactions from theindividual LCRs.

Analyzer Process Examines the completed transactions,identifying dependencies between the different transactions.

Coordinator Process Assigns transactions to the Applierprocess, monitor dependencies between the transactions andauthorize the commit of changes to the logical standby database.

Applier Process Apply the changes into the database andcommit the transactions.

LSP Continues


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PROTECTION LEVELS

The Protection Levels define how the Primary functions in thestandby configuration. They are:

Maximize Protection

Maximize Availability

Maximize Performance

Each one has a defined set of rules.


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PROTECTION MODES

Protection Mode Failure Protection Redo Shipping

Maximum Protection

Zero Data Loss

Protects Against Primary

and Network FailureLGWR using SYNC

and SRL


Failure

LGWR using SYNCMaximum Availability

Zero Data Loss

Best Effort Against Primary

Failure

ARCH or LGWR

using ASYNC

Maximum

Performance


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MAXIMUM PROTECTION MODE



and Network Failure

LGWR using SYNC

and SRL

Maximum Protection

Zero Data Loss

Zero Data Loss! ;

Highest Level of Protection;

Configuration: LGWR SYNC, SRLs;

Enforces protection of every transaction;

If last standby is unavailable, processing stops at primary;

Good for financial systems where no data loss is acceptable;

ALTER DATABASE SET STANDBY TO MAXIMIZEPROTECTION;


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MAXIMUMAVAILABILITY MODE



Failure

LGWR using SYNC

and SRL

Maximum Availability

Zero Data Loss

Zero Data Loss! as long as the network stays up!;

Configuration: LGWR SYNC, SRLs;

Enforces protection of every transaction;

If last standby is unavailable, processing continues at primary;

When the standby becomes available again, synchronizationwith the primary is automatic

ALTER DATABASE SET STANDBY TO MAXIMIZEAVAILABILITY;


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MAXIMUM PERFORMANCE MODE


Best Effort Against

Primary Failure

ARCH or LGWR

using ASYNC

Maximum

Performance

Highest Level of Performance;

Configuration: LGWR ASYNC or ARCH;

Protects from failure of any single component;

Least impact on production system;

Useful for applications that can tolerate some data loss.

ALTER DATABASE SET STANDBY TO MAXIMIZEPERFORMANCE;


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DATAGUARD SERVICESRedo Transport Services

Control the automated transfer of redo data from the production database to one ormore archival destinations

Log Apply Services

Redo data would be applied either from archived redo log files, or, if real-time applyis enabled, directly from the standby redo log files as they are being filled, withoutrequiring the redo data to be archived first at the standby database.

Role Transitions

Switchover

Role reversal between the primary database and one of its standby databases. Thisis typically done for planned maintenance of the primary system

During a switchover, the primary database transitions to a standby role, and the

standby database transitions to the primary role.

Failover

Occurs, when the primary database is unavailable.

Failover is performed only in the event of a catastrophic failure of the primarydatabase, and the failover results in a transition of a standby database to the primary.


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HIGH LEVEL

Broader perspective, Data Guard comprises of two parts:

REDO APPLY (DR)

Maintains a physical, block for block copy of the

Production (also called Primary) database.

SQL APPLY (Reporting)

Maintains a logical, transaction for transaction copy of the

Production database.


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DATAGUARD REDOAPPLY: BEST FOR DR

Data Guard Broker

PrimaryDatabase

Physical StandbyDatabase

Optional

Delay

Sync or AsyncRedo Shipping

Network

Redo Apply

DIGITALDAT A STORAGE

Backup

Physical Standby Database is a block-for-block copy of the primarydatabase

Uses the database recovery functionality to apply changes

Can be opened in read-only mode for reporting/queries

Can also perform backup, offloading production database

The best solution for DR

Sync or AsyncRedo Shipping Redo ApplyRedo Apply


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DATAGUARD SQL APPLY

Optional

Delay

AdditionalIndexes &

MaterializedViews

Sync or AsyncRedo Shipping

Network

ContinuouslyOpen for Reports

Data Guard BrokerPrimaryDatabase Logical Standby

Database

Logical Standby Database is an open, independent, active database

Contains the same logical information (rows) as the production database

Physical organization and structure can be very different

Can host multiple schemas

Can be queried for reports while logs are being applied via SQL

Can create additional indexes and materialized views for better queryperformance

Not all Data Types supported (See the manual for a list)


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REDO DATATRANSMISSION HOW?

Redo data could transferred from Primary to Standby by any

one of the following way:

Using Archiver Processes (ARCn) to Archive Redo Data.

Using the Log Writer Process (LGWR) to Archive Redo

Data.

By default, redo transport services use ARCn processes to

archive the online redo log files on the primary database.

ARCn archival processing supports only the maximum

performance level of data protection in Data Guardconfigurations.

LGWR process would be used to transmit redo data to standby

locations that operate in other data protection modes.


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DATAGUARD

ARCH REDO TRANSMISSION

ARC0 ARC1

Online

Redo

Log

LGWR RFS

Standby

Redo

Log

ARCn

Archived

Redo

Logs

MRP

LSPStandby

Database

Primary

Database

LOG_ARCHIVE_DEST_1

Primary Database Standby Database

Archived

Redo

Logs


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DATAGUARD

LGWR (ASYNC) REDO TRANSMISSION

Archived

Redo

Logs

ARCn

RFS

Standby

Redo

Log

ARCn

Archived

Redo

Logs

MRP

LSPStandby

Database

Primary

Database

LOG_ARCHIVE_DEST_1


LNSn

LGWR

Online

Redo

Log


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DATAGUARD

LGWR (SYNC) REDO TRANSMISSION

Archived

Redo

Logs

ARCn

Online

Redo

Log

RFS

Standby

Redo

Log

ARCn

Archived

Redo

Logs

MRP

LSPStandby

Database

Primary

Database

LOG_ARCHIVE_DEST_1


LNSnLGWR


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DATAGUARD ROLE TRANSITIONS

There are two types of role transition

Switchover

Planned failover to standby database

Original primary becomes new standby

Original standby becomes new primary

No data loss

Can switchback at any time

Failover

Unplanned failover to standby database

Original standby becomes new primary

Original primary may need to be rebuilt

Possible data loss


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DATAGUARD SWITCHOVER

After SwitchoverBefore Switchover

Primary

Instance

Database

Primary

Database

Site1

Database

Physical

Standby

Instance

Standby

Database

Site2

Standby

Database

Physical

Standby

Instance

Database

Site1

Database

Primary

Instance

Primary

Database

Site2

Redo Redo


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DATAGUARD FAILOVER

Database

Physical

StandbyInstance

Standby

Databas

Site2

After FailoverBefore Failover

Primary

Instance

Database

Primary

Database

Site1

Database

Physical

Standby

Instance

Standby

Database

Site2

Unavailable

Primary

Instance

Database

Site1

Database

Primary

Instance

Primary

Database

Site2

Redo Redo


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REDOAPPLY OR SQL APPLY..?

Maintains a physical, block-for-

block copy of the primary.

Can be open for read-only

queries.

At role transition, offers the

assurance that the standby

database chosen to be the new

primary has not been changed

compared to the old primary.

Can be used for backups

Faster, since it bypasses the

SQL transformation layer.

Maintains a logical,

transaction-for-transaction

copy of the primary.

Allows creation of additionalobjects, modification of

objects.

Possible to skip apply on

certain objects.

Can be used as a goodreporting solution supports

real-time reporting in 10g.

Has data type restrictions.

SQLApplyRedo Apply


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PHYSICAL STANDBY - CONFIGURATION

Step Up Overview:

Step 1 - Prepare the Primary for Standby

Step 2 - Copy the necessary files to standby system

Step 3 - Configure the Standby Parameters

Step 4 - Configure OracleNet

Step 5 - Startup the Standby Site

Step 6 - Begin Shipping and Applying Redo


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CONFIGURATION

Attached the document which has Step-by-Stepconfiguration of Physical Standby Database.

Microsoft Office

Word Document


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LOGICAL STANDBY - CONFIGURATION

Step Up Overview:

Step 1 - Prepare the Primary for Standby

Step 2 - Copy the necessary files to standby system

Step 3 - Configure the Standby Parameters

Step 4 - Configure OracleNet

Step 5 - Startup the Standby Site

Step 6 - Begin Shipping and Applying Redo


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CONFIGURATION

Attached the document which has Step-by-Stepconfiguration of Logical Standby Database.

Microsoft Office

Word Document


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ROLE TRANSITION - SWITCHOVER INVOLVES

PHYSICAL

STANDBY

DATABASE

Step Up Overview:

Step 1 Resolve the archived log Gaps.

Step 2 Verify the status of the databases to Switchover.

Step 3 Adjust the initialization parameters.

Step 4 Perform the switchover.


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SWITCHOVER INVOLVES PHYSICAL

STANDBY DATABASE .

Attached the document which has Step-by-Step configurationto perform switchover with Physical Standby Database.

Microsoft Office

Word Document


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ROLE TRANSITION - SWITCHOVER INVOLVES

LOGICAL STANDBY DATABASE

Step Up Overview:


Step 2 Verify the status of the databases to Switchover.


Step 4 Perform the switchover.


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SWITCHOVER INVOLVES LOGICAL

STANDBY DATABASE .

Attached the document which has Step-by-Step configurationto perform switchover with Logical Standby Database.

Microsoft Office

Word Document


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ROLE TRANSITION - FAILOVER INVOLVES

PHYSICAL STANDBY DATABASE

Step Up Overview:



Step 3 Initiate the Failover.

Step 4 Covert the Database Roles.

Step 5 Backup the new Primary Database.

Step 6

Optionally, Restore the failed Primary Database.


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FAILOVER INVOLVES PHYSICAL

STANDBY DATABASE .

Attached the document which has Step-by-Step configurationto perform failover with Physical Standby Database.

Microsoft Office

Word Document


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ROLE TRANSITION - FAILOVER INVOLVES

LOGICAL STANDBY DATABASE

Step Up Overview:



Step 3 Initiate the Failover.

Step 4 Covert the Database Roles.

Step 5 Recover the other Standby Databases.

Step 6

Backup the new Primary Database.Step 7 Optionally, Restore the failed Primary Database.


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FAILOVER INVOLVES LOGICAL STANDBY

DATABASE .

Attached the document which has Step-by-Step configurationto perform failover with Logical Standby Database.

Microsoft Office

Word Document


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SUMMARY.!!!

Data Guard provides an automated standby database whichcan essentially eliminate downtime of your production data.

Setup is easy and fairly straightforward.

Maintenance is minimal.

Switchovers and failovers can be done within a few minutes.

Reporting can be offloaded to the standby to ease theworkload on the primary.

And It's Free! (Included with Enterprise Edition)

Oracle Data Guard by Nagaraj Ramamurthy_97

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