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© Puget Sound Oracle Users GroupEducation Is Our Passion

PSOUG EducationEducation Is Our Passion

Hands-on Workshop Series

Oracle DataGuard 10gR2


Daniel A. [email protected]


We Do Not Practice:

Slow Death by PowerPoint


DiscussionOracle Data Guard Overview


Data Guard History

7.3: Custom Standby Database

8i: Automated Standbyread-only databasemanaged recoveryremote archiving

8i: Data GuardAutomationSingle command switch-overSingle command fail-overOracle Parallel Fail Safe (OPFS) 1993

1997Oracle8i

Oracle8Oracle7

1999

Oracle9i20012004 Oracle 10g

2007 Oracle 11g


Data Guard History

9iR1: Data GuardIntegrated zero-data-loss capabilityData Guard Broker w/ Data Guard Manager GUICommand Line Interface (CLI)Switchover and Failover operationsAutomatic gap resolutionAutomatic Synchronization

9iR2: Data GuardLogical standby databasesMaximum protection / availabilityEnhanced Data Guard BrokerCascaded redo log destinations

19931997

Oracle8iOracle8

Oracle7

1999


2007 Oracle 11g


Data Guard History10gR1: Data Guard

Real-time applyRecovery through OPEN RESETLOGSSimplified configuration with VALID_FOR attributeStandby redo log support on logical standby databasesImproved redo transmission securityImproved support for RACZero downtime instantiationof logical standby databases

10gR2: Data GuardFast-start FailoverFlashback Database across Data Guard switchoversAsynchronous Redo TransmissionFaster Redo Apply failover 1993

1997Oracle8i

Oracle8Oracle7

1999


2007 Oracle 11g


Fast Start FailoverFast-start failover: Automatically, quickly, and reliably fail over to a designated, synchronized standby databaseAfter a fast-start failover occurs, the old primary database is automatically reconfigured as a new standby database upon reconnection to the configuration. Maintain uptime and increase the availability, as well as the robustness of disaster recovery.Less need for manual intervention.


Flashback Database across Switchovers

It is now possible to flash back the primary and standby databases to an SCN or a point in time prior to a switchover operation. When you use this feature of Flashback Database on a physical standby database, the standby role is preserved. On a logical standby database, the role of the standby database is changed to what it was at the target SCN or time.


Asynchronous Redo TransmissionAsynchronous redo transmission using the log writer process (LGWR ASYNC) has been improved to reduce the performance impact on the primary database. During asynchronous redo transmission, the network server (LNSn) process transmits redo data out of the online redo log files on the primary database and no longer interacts directly with the log writer process.Allows the log writer process to write redo data to the current online redo log file and continue processing the next request without waiting for interprocess communication or network I/O to complete.


DiscussionData Guard Concepts


Causes of Data Loss

Source: Disaster Recovery Journal

Natural disasters 3%

Software corruption 4%

Computer viruses 7%

Human errors 36%

Hardware & system errors 49%


Fault Tolerance

Real Application ClustersReal Application ClustersContinuous Availability for all ApplicationsContinuous Availability for all Applications

Data Data GuardGuardGuaranteedGuaranteed Zero Data Zero Data LossLoss

FlashbackFlashbackGuaranteedGuaranteed Zero Data LossZero Data Loss

SystemMaintenance

PlannedDowntime Database

Maintenance

Dynamic ReconfigurationDynamic ReconfigurationCapacity on Demand without InterruptionCapacity on Demand without Interruption

Online RedefinitionOnline RedefinitionAdapt to Change OnlineAdapt to Change Online

ASM MirroringASM MirroringStorage Failure ProtectionStorage Failure Protection

HumanError

SiteFailures

Storage/NetFailures

UnplannedDowntime

SystemFailures


Data Guard Acronyms

ARC0 ArchiverDMON Data Guard MonitorFAL Fetch Archive LogLCR: Logical Change RecordLGWR Log Writer backend processLSP: Logical Standby Process aka SQL Apply (logical)

MRP Managed Recovery Process aka Redo Apply (physical)

RFS Remote File Server (receives undo)

TAF Transparent Application Failover


A Complete High-Availability Solution

Recovery Manager (RMAN)Flashback Database / Query / TableStreams ReplicationGrid ControlReal Application Clusters (RAC)Data Guard

Data Guard is one part of a complete HA solution


What is Data Guard?

Real-time replicationPrimarily intended for replication between data centersUtilizes Log Miner to read redo logsShips redo to remote site via Advanced QueuingMost often applies changes to a standby databaseCan cascade changes from standby-to-standby

Built by the same team that wrote RMAN, Streams, and Change Data Capture


Why Data Guard?

High Availability (HA) Disaster PreparationReplication between geographically separated data centers

Transparent Application Failover (TAF) Remove backup process overhead from primary production systemsRolling hardware and operating system upgrades and system maintenanceRolling database upgrades and patchingProduction mirror for reportingSystem migration (for example to ASM)


What is a Standby DatabaseA copy of a production database that you can use for disaster protection. You can update the standby database with archived redo logs from the production database in order to keep it current. If a disaster destroys the production database, you can activate the standby database and make it the new production database.You can maintain the standby data in one of the following modes:

For physical standby databasesRedo ApplyOpen read-only mode

For logical standby databasesOpen read/write mode

A Standby Database is NOT Data Guard


Types of Standby DatabasesThere are two types of standby databases

Physical standby databaseblock-for-block identical with the primary databaseSynchronized with the primary database by application of redo data

Logical standby databaseShares the same schema definitionSynchronized with the primary database by transforming the data in the redo received from the primary database into SQL statements that are executed


Oracle Data Guard Architecture

Network Broker

ProductionDatabase

Logical StandbyDatabase Open for

Reports

SQLApply

Transform Redo to SQL

AdditionalIndexes & MVs

Physical StandbyDatabase

DIGITAL DATA STORAGE

DIGITAL DATA STORAGE

Backup

Redo Apply

Sync or Async Redo Shipping


Database Protection Modes

Maximum ProtectionNo Data Loss and No data divergenceArch_dest: mandatory, lgwr, sync, affirmPrimary db shutdown when unable to access stdby

Maximum AvailabilityArch_dest: mandatory, lgwr, sync, affirmProtection auto lowered when stdby is unavailable

Maximum PerformanceArch_dest: lgwr/arch, sync/async, mandatory/optionalMinimal performance impact


Protection Modes and Requirements

No Yes for ASYNCASYNC or SYNC

MAXPERFORMANCE

YesYes SYNCMAXAVAILABILITY

No Yes SYNCMAXPROTECTION

Used with Fast-Start Failover?

Standby Redo Log Files Needed?

Redo Transport

Protection Mode


Data Guard Services

Log transport servicesConfigurable using ARCH or LGWRUsed by Data Guard and Streams

Log apply servicesRedo Apply (Physical Standby)

Recovers the redo data received from the primary database and applies the redo to the physical standby database.

SQL Apply (Logical Standby)Transforms the data in the redo received from the primary database into SQL statements and then executes the SQL statements on the standby database.

Role-management serviceswhat do it do?


DiscussionData Guard Architecture

Physical Standby


PSOUG Lab Topology

Public Network

Production

Data Center 1

Public Network

10/100 Ethernet Switch

Standby

Data Center 2

GigEthernet Switches

Separate Storage

End Users Connecting Directly or Through An

Application Server


Oracle Data Guard: Architecture

LGWR

Primary database

transactions

Onlineredologs

ARC0

FAL

RFS

MRP or LSP

Archived redo logs

ARC0

Standbydatabase

Reports

(MRP only)

Standbyredo logs

Archived redo logs

BackupOra

cle

net


Standby Redo Logs

Redo from primary database

RFS ARC0

Standbyredo logs

Archivedredo logs

MRP/LSP

Standby database


Physical Standby Database

Public Network

Production

Data Center 1

Public Network

Standby

Data Center 2

Redotransport Redo

apply

Redo stream


Application ServerTo Either or Both


Logical Standby Database

Public Network

Production

Data Center 1

Public Network

Standby

Data Center 2


Application ServerTo Either or Both

Transform redo into SQLand execute

Reports


Redo records

LCRLCR

:

Shared pool

Transaction groups

Transactions sorted in

dependency order

Log Mining

Apply processing

Logical change records not grouped into transactions

Transactions to be applied

Reader Preparer Builder

AnalyzerCoordinatorApplier

Data files

Redo data from primary database

SQL Apply Process: Architecture


Real Time Apply

Redo data is applied to the standby database as soon as it is received from the primary database

In Oracle9i Data Guard this apply has to wait till an archivelog iscreated on the standby database

For Redo Apply:ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE

For SQL Apply:ALTER DATABASE START LOGICAL STANDBY APPLY IMMEDIATE

When real time apply is enabled, RECOVERY_MODEcolumn in V$ARCHIVE_DEST_STATUS displays “MANAGED REALTIME APPLY”


Real-Time Apply

RFS

Standbyredo log

files

MRP or LSP

ARC0

Primary database

Standby database

Archivedredo log

files


Real-Time Apply Architecture

PhysicalLogicalStandbyDatabase

MRP/ LSPRFS

StandbyRedo Logs

ARCH

Archived Redo Logs

Archived Redo Logs

PrimaryDatabase

Transactions

LGWR

Online Redo Logs

ARCH

Oracle Net

Real Time Apply


Real Time Apply – Benefits

Standby databases now more closely synchronized with the primary

More up-to-date, real-time reportingFaster switchover and failover times

Reduces planned and unplanned downtimeBetter Recovery Time Objective (RTO) for DR


DiscussionData Guard Configurations


Data Guard Role Transitions

SwitchoverPlanned role reversalUsed for OS or hardware maintenance

FailoverUnplanned role reversalUse in emergencyZero or minimal data loss depending on choice of data protection mode

Role-transition operations are not automatically invoked


Maximum Availability Architecture

RAC productiondatabase

RAC physicalstandby database

Oracle Application

Server

Oracle Application

Server

WAN traffic manager

Clients

Data Guard RAC logical

standby database


The “Black Line”

Determine Configuration

Build Primary Data Center

Build Failover Data Center

Activate Replication


Oracle Data Dictionary (1 of 2)

SQL> SELECT object_name2 FROM dba_objects3 WHERE object_name LIKE '%LOGSTDBY%';

DBA_LOGSTDBY_EVENTSDBA_LOGSTDBY_HISTORYDBA_LOGSTDBY_LOGDBA_LOGSTDBY_NOT_UNIQUEDBA_LOGSTDBY_PARAMETERSDBA_LOGSTDBY_PROGRESSDBA_LOGSTDBY_SKIPDBA_LOGSTDBY_SKIP_TRANSACTIONDBA_LOGSTDBY_UNSUPPORTEDDBMS_INTERNAL_LOGSTDBYDBMS_LOGSTDBYDBMS_LOGSTDBY_LIBGV$LOGSTDBYGV$LOGSTDBY_PROCESSGV$LOGSTDBY_PROGRESSGV$LOGSTDBY_STATEGV$LOGSTDBY_STATSGV$LOGSTDBY_TRANSACTIONGV_$LOGSTDBYGV_$LOGSTDBY_PROCESSGV_$LOGSTDBY_PROGRESSGV_$LOGSTDBY_STATEGV_$LOGSTDBY_STATSGV_$LOGSTDBY_TRANSACTIONLOGSTDBY$APPLY_MILESTONE

LOGSTDBY$APPLY_PROGRESSLOGSTDBY$EVENTSLOGSTDBY$EVENTS_INDLOGSTDBY$HISTORYLOGSTDBY$PARAMETERSLOGSTDBY$PLSQLLOGSTDBY$SCNLOGSTDBY$SKIPLOGSTDBY$SKIP_SUPPORTLOGSTDBY$SKIP_TRANSACTIONLOGSTDBY_LOGLOGSTDBY_SUPPORTLOGSTDBY_UNSUPPORTED_TABLESV$LOGSTDBYV$LOGSTDBY_PROCESSV$LOGSTDBY_PROGRESSV$LOGSTDBY_STATEV$LOGSTDBY_STATSV$LOGSTDBY_TRANSACTIONV_$LOGSTDBYV_$LOGSTDBY_PROCESSV_$LOGSTDBY_PROGRESSV_$LOGSTDBY_STATEV_$LOGSTDBY_STATSV_$LOGSTDBY_TRANSACTION


Oracle Built-in PackagesSQL> SELECT DISTINCT object_name, overload2 FROM all_arguments3 WHERE package_name = 'DBMS_DRS‘4 ORDER BY 1,2;

OBJECT_NAME OVERLOAD------------------------------ --------CANCEL_REQUESTDELETE_REQUESTDG_BROKER_INFODO_CONTROL 1DO_CONTROL 2DO_CONTROL_RAW 1DO_CONTROL_RAW 2DUMP_METAGETMIVGET_PROPERTYGET_PROPERTY_OBJGET_RESPONSEGET_RESPONSE_RAWPINGREADYTOFAILOVERSLEEPSTATECHANGERECORDED


Identifying Destination Settings

SQL> SELECT DEST_ID,VALID_TYPE,VALID_ROLE,VALID_NOW2 FROM V$ARCHIVE_DEST;

DEST_ID VALID_TYPE VALID_ROLE VALID_NOW------- --------------- ------------ --------------

1 ONLINE_LOGFILE ALL_ROLES YES2 STANDBY_LOGFILE STANDBY_ROLE YES3 ALL_LOGFILES ALL_ROLES UNKNOWN4 ALL_LOGFILES ALL_ROLES UNKNOWN5 ALL_LOGFILES ALL_ROLES UNKNOWN6 ALL_LOGFILES ALL_ROLES UNKNOWN7 ALL_LOGFILES ALL_ROLES UNKNOWN8 ALL_LOGFILES ALL_ROLES UNKNOWN9 ALL_LOGFILES ALL_ROLES UNKNOWN10 ALL_LOGFILES ALL_ROLES UNKNOWN11 ALL_LOGFILES ALL_ROLES YES

11 rows selected.


Closing Remarks

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