The document discusses Oracle Data Guard, a disaster recovery solution for Oracle databases. It provides: 1) An overview of Data Guard, explaining that it maintains a physical or logical standby copy of the primary database to enable failover in the event of outages or disasters. 2) Details on the different types of standby databases - physical, logical, and snapshot - and how they are maintained through redo application or SQL application. 3) The various Data Guard configuration options like real-time apply, time delay, and role transitions such as switchover and failover.

1. Oracle Data Guard for BeginnersProduct Manager for Database Monitoring
Feb 21st , 2019
Pini Dibask
RMOUG
Training Days
2019

2. Confidential2
• Pini Dibask, Product Manager for Database Tools, Quest Software
• Oracle ACE
• Oracle Certified Professional DBA (OCP)
• Public Speaker: Oracle OpenWorld, IOUG Collaborate, DOAG, OUGN, AOUG
• Blogger: OracleDBPro.BlogSpot.com
Pini.Dibask@Quest.com
http://Linkedin.com/in/pinidibask
@pini_dibask
About the Speaker

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Who is Quest Software?
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software
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m e m b e r s
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Quest is a global software provider trusted by
100,000 customers and 6,000 partners in 100
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We help IT organizations spend less time on
administration and more time on innovation.
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partners selling
our software

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• Toad database development &
management tools
• Foglight & Spotlight database
performance monitoring
solutions
• SharePlex for heterogeneous
database replication
Quest Database Management Solutions

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Agenda
• HA & DR Basic Concepts
• High-Level Overview of Oracle Data Guard
• Types, Modes, and Options
• Data Guard Limitations
• Monitoring
• New Features

6. HA and DR
Basic Concepts01

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 Ensuring high level of SLA (Service Level Agreement)
 Enforcing the organization’s Data Protection policy
 RPO (Recovery Point Objective)
 RTO (Recovery Time Objective)
RPO RTO
Disaster OccursRestore Point Up and Running
Maximum amount of data a
business can allow itself to lose
Maximum amount of downtime
a business can incur until the
system is up and running again
16:3016:00 17:00
Recovery Service Objectives

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Oracle Database HA & DR Solutions
Server Failures
Storage Failures
Site Failures
Corrupted Files
Missing Files
Human Errors
RAC & RAC One Node
Failover Clusters
ASM Normal Redundancy
ASM High Redundancy
Oracle Golden Gate
RMAN
User Managed Backups
Flashback Features
In which types of
failures Data Guard
can help?

9. Overview of Oracle
Data Guard
02

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What is Oracle Data Guard (High Level)?
Primary
database
Standby
database
Database Database copy
Redo transport
OracleNet

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Why Use Oracle Data Guard?
 Complete data protection against corruption and data loss
 Continuous service during disasters or crippling data failures
 Efficient use of system resources
 Flexible configuration to meet business requirements
 Centralized management
 Integration with Oracle Database

12. Data Guard Types,
Modes and Options
03

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Standby Database Types
 Physical Standby Database
o Identical to the primary on a block-by-block basis (redo apply)
 Logical Standby Database
o Not identical at the block level (SQL Apply)
 Snapshot Standby Database
o Fully read/write standby database
o Created by converting a physical standby database

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Physical Standby – Redo Apply Architecture
Production
database
Physical standby
database
Redo
apply
Redo
stream
Redo
transport
Backup
Physical standby
database
Primary
database

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Logical Standby – SQL Apply Architecture
Primary
database
Redo transport
Transform redo
information into
SQL
SQL
Apply
Reports
Production
database
Logical standby
database
Logical standby
database

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Standby Database Types
Parameter Physical Standby Logical Standby
Methodology Identical to primary on a
block-by-block basis
Shares same logical information
How it works? Redo Apply SQL Apply
Can be used for reporting? With extra licensing Yes (open read-write mode)
Fast incremental backups via
change tracking
Yes No
Performance Best - redo apply Doesn’t bypass SQL code layers
Support all Data Types? Yes No

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Active Data Guard
 Introduced in Oracle Database 11g
 Receives and applies redo while standby is open for read-only access
 Enables physical standby to be used for both protection and reporting
 Automatic corruption repair
 Option for Oracle Enterprise Edition

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Snapshot Standby Databases
 Fully updatable (read/write) standby database
 Can be used for testing purposes
 Created by converting a physical standby database
 Receives redo from the primary database, but does not apply the redo
 When testing is finished, can be converted by using flashback database

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Types of Data Guard Services
Redo Transport Services
oControls the automated transmittal of redo from primary to standby
Apply Services
oRedo Apply
oSQL Apply
Role Management Services
oChanges primary & standby roles due to planned or unplanned transition

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Applying Services Configurations
 Real-Time Apply
 By default, apply services wait for redo log to be archived before applying
 It’s possible to apply redo immediately via standby redo logs
 Specifying Time Delay
 Option to create a time lag
 Specified in minutes
 Protects against undesired DMLs/DDLs

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Oracle Data Guard Architecture
Primary database
transactions
MRP or
LSP
Standby
database
Archived redo
logs
Backup
Online
redo
logs
ARC0
RFS
Archived redo
logs
ARC0 Reports
Standby
redo logs
Oraclenet
LNSn
(Real-time
apply)
LGWR
Redo
buffer
Gap resolution

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Primary Database Processes
Primary database
transactions
MRP or
LSP
Standby
database
Archived redo
logs
Backup
Online
redo
logs
ARC0
RFS
Archived redo
logs
ARC0 Reports
Standby
redo logs
Oraclenet
LNSn
(Real-time
apply)
LGWR
Redo
buffer
Gap resolution

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Standby Database Processes
Primary database
transactions
MRP or
LSP
Standby
database
Archived redo
logs
Backup
Online
redo
logs
ARC0
RFS
Archived redo
logs
ARC0 Reports
Standby
redo logs
Oraclenet
LNSn
(Real-time
apply)
LGWR
Redo
buffer
Gap resolution

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 Switchover
oPlanned role reversal
oUsed for OS or hardware maintenance
 Failover
oUnplanned role reversal
oEmergency use
oZero or minimal data loss (depending on choice of data protection mode)
oCan be initiated automatically when fast-start failover is enabled
Role Transitions

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Switchover : Before
Standby
database
Read/write
transactions
Primary
database
San Francisco
Boston
Oracle Net
Application
Application
Read-only
reports

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Switchover : After
Standby
database
Read/write
transactions
Primary
database
Application
Application
Read-only
reports
San Francisco
Boston
Oracle Net

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Failover
Standby
database becomes
primary database.
Read/write
transactions
Online redo
logs
Local
archiving
San Francisco
Boston
Archived redo
logs
Application
Online Redo
Logs
Local
Archiving
Archived redo
logs
Primary database

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Types of Failover
 Manual failover: Invoked by the DBA
o Complete: Minimize data loss by applying all available redo on the standby database
o Immediate: No additional data is applied on the standby database
 Fast-start failover: Invoked automatically by the Data Guard broker
 Uses observer - separate client side component
 Monitors fast-start failover environments

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Oracle Observer

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Failover Considerations
 Failover should be used only in an emergency
 Old primary database will no longer be a part of the configuration
 Possible data loss - depends on the data protection mode
 When choosing standby to failover, use the most current

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Data Protection Modes
 Maximum Performance (Default)
o Transaction commits as soon as redo written to the local redo log (ASYNC)
o Data Loss: Possible
 Maximum Protection
o Transaction commits only when redo written to at least one standby redo log (SYNC)
o If no acknowledge from standby, Oracle shuts down primary database
o Data Loss: Not Possible
 Maximum Availability
o Highest level of data protection without compromising the availability of the primary database
o If primary cannot write redo to at least one standby, it operates as in maximum performance
o Data Loss: Possible

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Data Protection Modes - Summary
Mode Risk of data loss Transport If no acknowledge from standby
Maximum
Protection
Zero Data Loss SYNC Stall primary until acknowledgement
received from standby
Maximum
Availability
Possible Data
Loss
SYNC Stall primary until acknowledgement
received from standby or timeout
threshold expires
Maximum
Performance
Possible Data
Loss
ASYNC Primary never waits for acknowledge

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Data Protection Modes - Key Considerations
 Maximum Performance = compromise on protection
 Maximum Protection = compromise on performance (usually)
 Better to use at least 2 standby databases when running maximum protection
 NET_TIMEOUT parameter of LOG_ARCHIVE_DEST_n=30 seconds (default)
 How to address the trade-off between Protection and Performance?

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FAR Sync - 12c Feature
Far Sync
Primary Remote
Standby
ASYNC - Alternate

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FAR Sync - 12c Feature
Redo
Far Sync
ASYNC
25ms
SYNCPrimary Standby
 Great for long-distance replication if data loss in not acceptable
 Lightweight and easy to deploy
 Requires Active Data Guard option

36. Data Guard Broker04

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Data Guard Broker Overview
 Distributed Data Guard management framework
 Automates the creation and maintenance of Data Guard environments
 Performs all management operations locally or remotely:
o DGMGRL (command-line interface)
o Oracle Enterprise Manager

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Data Guard Broker Architecture
Primary site
Standby site 9
Standby site 2
Graphical user interface
or
command-line interface
DMON
Archived
redo logs
Online
redo logs
Standby site 1
Oracle
Net Standby
redo logs
Archived
redo logs
Log
apply
services
Data Guard Configuration
Log
transport
services
Primary
database
DMON
Configuration
files
Configuration
files Standby
database
Standby
redo logs
Online
redo logs
 Client Side
o DGMGRL
o OEM
 Server Side
o DMON process
o Configuration files

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Configuration Management With vs. Without Data Guard Broker
Parameter With Broker Without Broker
General Manage Databases as
one
Manage Databases separately
Creation of the standby database Intuitive via OEM Manual process
Configuration & Management Configure and manage
from a single interface
Each database separately
Control role transitions Invoke role transition
with a single command
Coordinate sequences of multiple
commands across database sites

40. Data Guard
Limitations05

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Data Guard will NOT be the right choice when…
 Replica database must be open read-write while synchronizing with the primary
 Active data guard is open read-only, not read-write
 Logical standby is open read-write, but target tables are available only for read-only operations
 Replication from recent to older Oracle release (for example - 12c to 11g)
o Compatible parameter must be set the to the same value on physical standby
o When using logical standby, compatible can have a lower value in the primary database
 Multi-master and bi-directional replication
 Cross-platform which are not supported by DataGuard (e.g. cross-endian replication)
 Oracle to Non-Oracle replication
 Non-Enterprise edition Databases

42. Consider alternatives when Data Guard does not fit
Flexible, industrial
strength replication
Half the total cost
of Oracle$ Unrivaled, award
winning support

43. Data Guard
Monitoring06

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Data Guard Monitoring via Dictionary Views
V$DATABASE - Displays general data guard information
Primary

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Data Guard Monitoring via Dictionary Views
V$DATABASE - Displays general data guard information Physical
Standby

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Data Guard Monitoring via Dictionary Views
V$ARCHIVE_DEST - View standby destination status

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Data Guard Monitoring via Dictionary Views
V$ARCHIVED_LOG - Archived redo logs that have been applied

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Data Guard Monitoring with Tools

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Data Guard Monitoring with Tools

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Data Guard Monitoring with Tools

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Additional Data Guard New Features
 Fast sync
 Multi-instance redo apply
 AWR Support for Standby Database

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Data Guard Summary
 Powerful and simple HA & DR solution
 Active Data Guard is my favorite option (requires a special license)
 Choose the right protection mode according to the business SLAs
 Use Data Guard Broker
 Be aware of Data Guard limitations
 Don’t forget to monitor…

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Quest provides your team with the tools to cover all of your
database platforms…
* Platform support varies from tool to tool

54. Questions?

55. Thank you