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Oracle Data Guard for Beginners
1. Oracle Data Guard for BeginnersProduct Manager for Database Tools
April 23rd , 2018
Pini Dibask
IOUG
Collaborate
2018
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
3. Confidential3
Who is Quest Software?
9 0 % o f
F o r t u n e 1 0 0
using our
software
1 , 5 0 0
engineers building
quality products
4 M
c o m m u n i t y
m e m b e r s
sharing best practices
3 , 5 0 0
employees focused
on customers
Quest is a global software provider trusted by
100,000 customers and 6,000 partners in 100
countries.
We help IT organizations spend less time on
administration and more time on innovation.
6 , 0 0 0
partners selling
our software
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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
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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?
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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
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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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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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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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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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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
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
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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
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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
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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
