daniela milanova - bgoug · rman_dataguard_10g_wp.pdf. data guard or remote mirroring?
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What is Data Guard?
• Management, monitoring and automation software infrastructure that protects data against failure, errors, and corruptions of the database
• Automates the process of maintaining a copy of a Oracle production database (standby database)
Data Changes
PrimarySite
Clients Clients
StandbySite
PrimaryDatabase
StandbyDatabase
Data Guard Architecture
Services types:• Log transport services• Log apply services• Role-management services
Software Data Guard Requirements
• Same release of Oracle Database Enterprise Edition must be installed for all databases
• Incase of using ASM/OMF, all should use the same combination
Hardware an OS Data Guard Requirements
• The hardware can be different for the primary and standby database
• The operating system and platform architecture for the primary and standby databases must be the same
• The operating system version for the primary and standby databases can be different
• In case of all databases are on the same system, OS must allow mounting more than one database with the same name.
Data Guard At the Highest Level
• Data Guard comprises of two parts• REDO APPLY
• Maintains a physical, block for block copy of the Production (also called Primary) database.
• Can be open in Read Only mode for short time reporting
• SQL APPLY• Maintains a logical, transaction for transaction
copy of the Production database.• Can be open in Read Write for reporting
purposes and cloning activities
REDO Apply Architecture
• Maintains a ‘Physical’ block for block copy of the Primary Database
Physical Standby DatabaseAsynchronous/Synchronous
Redo Shipping
PrimaryDatabase
Network
DIGITAL DATA STORAGE
DIGITAL DATA STORAGE
Backup
Redo Apply
MRP
SQL Apply Architecture
Logical Standby Database
ContinuouslyOpen for Reports
SQLApply
TransformRedo to
SQLAdditional
Indexes and Materialized
Views
• Maintains a ‘Logical’ transactional copy of the Primary Database
Asynchronous/Synchronous
Redo Shipping
PrimaryDatabase
Network
Data Changes
PrimarySite
Clients
ReportingClients
StandbySite
PrimaryDatabase
LogicalStandbyDatabase
Data Protection & Disaster Recovery Solution with Reporting Capability
Data Changes
StandbySite
PhysicalStandbyDatabase
DataGuard
Data Guard Data Protection Modes
• Maximum protection• No data loss• In case of failure remote writting the primary
database is shutsdown
• Maximum availability• No data loss• In case of failure remote writting the primary
database works in maximum performance
• Maximum performance• Highest possible level of data protection• No affecting performance of the primary database
Data Guard Role Transition• Oracle Data Guard supports two role-
transition operations• Switchover
• Planned role reversal• Used for OS or hardware maintenance• No data loss
• Failover• Unplanned role reversal• Use in Emergency• Zero or minimal data loss depending on choice
of data protection mode
Existing Site Recovery Tradeoffs
• Log apply may be delayed to protect from user errors but:• Switchover/Failover gets delayed• Reports run on old data
• After failing over to standby, production DB must be rebuilt
Primary Database Standby DatabaseRedo
Shipment
DelayedApply
Reporting on delayed data
Enhanced DR with Flashback Database
• Flashback DB removes the need to delay application of logs• Flashback DB removes the need to reinstantiate primary after
failover• Real-time apply enables real-time reporting on standby
Real Time Apply
No Delay!
Real TimeReporting
Flashback Log
Flashback Log
Primary: No reinstantiation after failover!
RedoShipment
Primary Database Standby Database
Rolling Database Upgrades
• In Oracle Database SQL Apply provides the starting point for performing rolling upgrades of the Oracle RDBMS software and database with minimal interruption of service.
• By utilizing a Logical standby database customers can upgrade one database while running on the original production database and then run in a mixed version environment before returning to the original, but upgraded, configuration!
SQL Apply – Rolling Database Upgrades
Major ReleaseUpgrades
Patch SetUpgrades
Cluster Software & Hardware Upgrades
Initial SQL Apply Config
ClientsRedo
Version X Version X
1
BA
Switchover to B, upgrade A
Redo
4
Upgrade
X+1X+1
BA
Run in mixed mode to test
Redo
3
X+1X
A B
Upgrade node B to X+1
Upgrade
LogsQueue
X
2
X+1
A B
Benefits of Oracle Disaster Recovery Solution
• Disaster recovery and high availability • Complete data protection • Efficient utilization of system resources • Flexibility in data protection to balance
availability against performance requirements
• Automatic gap detection and resolution • Centralized and simple management • Integrated with Oracle database
Ease of Use
• New and Improved Data Guard Manager!• Monitoring SQL Apply
• Unsupported Storage Attributes• Applied Logs and Apply Progress
• Managing the Logical Standby• Bypassing the Guard• Skipping Table Redo• Skipping Failed (and subsequently
fixed) Transactions
New Data Guard Feature:Fast-Start Failover
Automatic and fast• Physical and Logical standby each complete
failover in less than 20 seconds• Old primary is reinstated automatically once
connectivity is re established between Observer and primary database
Data Guard Best Practices:Switchover for Planned MaintenanceFor fastest switchover (< 1 minute)• Prior to switchover
• A physical standby transitioning from read-only back to Redo Apply should be restarted
• Disconnect all sessions and stop job processing• Shutdown abort for all secondary RAC instances on both primary
and standby databases• Enable real-time apply on the standby database and ensure the
standby is synchronized with the primary database• For switchovers using SQL or command line interface,
open the new primary directly from the mount state• Or, simulate a Fast-Start Failover - complete transactions
and shutdown abort all primary instances
Data Guard Best Practices:Faster Redo Transport
• Set SDU=32K• Tune network parameters that affect network
buffer sizes and queue lengths• Ensure sufficient network bandwidth for peak
database redo generation rate + other activities
http://www.oracle.com/technology/deploy/availability/pdf/MAA_DG_NetBestPrac.pdf
Data Guard Best Practices:Tune Network Parameters
• Send and receive buffer size = 3 x bandwidth delay product (BDP)
BDP = the product of the estimated minimum bandwidth and the round trip time between the
primary and standby serverBDP = 1,000 Mbps * 25ms (.025 secs)
= 1,000,000,000 * .025= 25,000,000 Megabits / 8 = 3,125,000 bytes
• Tune network device queues to eliminate packet losses and waits. Set device queues to a minimum of 10,000 (default 100)
Impact of Network Tuning
Test Results - Oracle Database10g Release 1 & 2Test Results - Oracle Database10g Release 1 & 2
Data Guard or Remote Mirroring• Remote Mirroring (host-based and storage-based)
is another way to protect enterprise data
• However:• What about Data Reliability?• What about Data Recoverability?• What about Data Availability?• What about Cost?
• A well-designed Business Continuity Plan must consider these critical issues in addition to simple data protection
1. Better Network Efficiency- Transmits only redo data
- Remote mirroring solutions: datafiles, archivelog files, redolog files must be mirrored
2. Better suited for WAN-s– Fibre/ESCON-based mirroring solutions have an intrinsic distance
limitation– Protocol converters needed – adds to the cost, complexity and
latency– Data Guard based on standard TCP/IP– Data Guard doesn’t have to deal with protocol converters, extra cost
and latency issues
3. Better Data Protection– Data Guard enables zero data loss– Preserves write-order consistency– Avoids logical and physical corruptions– Both SQL Apply and Redo Apply validates redo data before applying
Data Guard is the Preferred Solution
Data Guard is the Preferred Solution4. Higher Flexibility
– Data Guard based on commodity hardware– Does not force lock-in with storage vendors– Remote mirroring solutions typically need identically configured
storage from the same vendor
6. Higher ROI– Provides more value for DR investment
� Standby database can be opened read-only or read-write � Allow backups to be offloaded on the standby database � Allows reporting/queries using the standby database
– Integrated natively with other HA features (RAC, RMAN, etc.)– No extra cost
5. Better Functionality– Data Guard is a comprehensive DR solution:
� Redo Apply/SQL Apply� Flexible protection modes� Push-button switchover/failover� Graceful handling of network connectivity problems
Data Guard and Remote Mirroring -Summary
• For protecting Oracle data, Oracle Data Guard’s integrated disaster recovery solution involving standby databases is preferred to remote disk mirroring:
• For technical reasons• For business reasons
• Remote mirroring may be used to protect non-Oracle database data that are changing frequently:
• File system data• Data in databases that are not Oracle
Competitive Strengths vs. SharePlex• SharePlex
• Redo log-based replication tool from Quest software
• Heavy front-end processing to extract transaction information from the primary redo logs
• Somewhat similar to Data Guard SQL Apply
• It doesn’t make sense for customers to use SharePlex:
No support because of architecture limitationsSupportedZero Data Loss
Much moreMinimalPrimary system overhead
Limited integrationIntegrated with RAC, RMAN, Flashback, …Integration with HA features
At best a replication solutionComprehensive and integrated DR solutionDR
Based on unpublished and unsupported interface1Native feature of the databaseFeature support
ExpensiveFreeCost
SharePlexData Guard
1. See MetaLink Note 97080.1
Data Guard Release 10.2Redo Transport Improvements• Increased network write sizes to 10 MB to better
utilize network capacity for both ARCH and LNS• LNS can potentially write 10MB or less
• Full decoupling of LGWR and LNS processes• No more waits during log switches• No more waits when LNS buffer is full
• Intra-file parallelism support for ARCH• Up to 29 parallel remote archive processes
Data Guard Best Practices:Gap Resolution and Data Loss• For fastest gap resolution
• Leverage intra-file archive parallelism (MAX_CONNECTIONS attr)• Follow tips for tuning redo transport to improve network
utilization• To minimize data loss
• For a low latency, high bandwidth network, use SYNC transport• For high latency or low bandwidth networks, use ASYNC to
minimize primary database performance impact• Follow tips for tuning redo transport• Example: Less than 7 seconds of data loss exposure for
high redo rates of 2-12 MB/sec with <=25 ms latency in our tests
Data Guard Best Practices:Reduce Overhead on Primary
Performance Gains with 10g Release 2 ASYNC Transport• For redo rates less than 2 MB/sec, there is less than 5%
impact on the primary database across different latencies
• For very high redo rates of 20 MB/sec, less than 10% impact on primary database even with latencies of 50 and 100 ms
• Primary database performance impact was 2-3 times less with the new ASYNC transport compared to previous releases
Best Practice• Allocate additional I/O bandwidth for Online Redo Log
Files
Data Guard Best Practices:Using Standby for Backups
Offload Backups to Physical Standby Database• Eliminate backup overhead on primary database• RMAN allows for backup operations while Redo Apply is
in progress Best Practices
• For simplicity, use identical directory structures on the primary and standby databases
• Use RMAN Recovery Catalog so that backups taken on one database server can be restored on another
• Use a catalog server physically separate from primary and standby sites
• Reference MAA RMAN/Data Guard best practices paperhttp://www.oracle.com/technology/deploy/availability/pdf/
RMAN_DataGuard_10g_wp.pdf
Data Guard or Remote Mirroring?
• Data Guard SYNC transport has less overhead on the primary database
Load 200txns/sec & Redo rate 1.1 MB/sec
Data Guard Advantage Because …• Data Guard only transmits redo. A remote
mirroring solution must transmit all database writes• A remote mirroring solution needs to transmit the
following writes: LGWR - log writer, DBWR – database writer, ARCH - archiver, RVWR – flashback log writer, and foreground direct writes
• Both DBWR and LGWR are affected by network latency in a remote mirroring solution. In contrast, only LGWR is impacted by network latency in a Data Guard solution• Higher wait times for DBWR can be very etrimental to
performance, causing contention for free buffers and an increase in buffer busy waits
First American Real Estate Solutions
• Nations largest source of Real Estate data• 100 million properties• Online services for 50,000 clients
• Lenders, Information Resellers, Government, Utilities, Corporations, Appraisers, Agents & Title Companies
• Thousands of concurrent online users at peak
• www.firstamres.com
HA/DR Requirements• High Availability: 24x7 - 365 days/year
• Limited instances of planned downtime once/quarter
• Recovery Point Objective (RPO) - maximum data loss
• Oracle9i: 10MB for computer failure, 200MB for site failure
• Recovery Time Objective (RTO) for Oracle Database• Oracle9i: 10 minutes for computer failure, 1 hour for site
failure
• Oracle Database 10g goals• RPO: zero data loss for computer failure, 10MB for site
failure• RTO: zero downtime for computer failure, 10 minutes for
site failure
First American Oracle 9i HA/DR Architecture
Primary Database
Local Standby #1Data GuardLGWR AsynchronousRedo Shipping
Remote Disaster Recovery Site
PrimaryProductionSite
Local Standby #2Data GuardDelayed Apply(30 minutes)LGWR AsynchronousRedo Shipping
RemoteStandby #3
Data GuardArchive Log Shipping (ARCH)
1500 miles >
Looking Ahead to Oracle Database 10g
• Real Application Clusters• Transparent failover on node failure, zero data loss
• Flashback Technologies• Flashback Database & Flashback Table • Protect/repair for logical corruptions
• Enhanced LGWR ASYNC redo transport• Improve RPO for remote DR site
• Real Time Apply• Improve RTO
First AmericanOracle Database 10g Architecture - Plan
Primary DatabaseReal Application Cluster
Data GuardLGWR Asynchronous
redo shipping
Remote DisasterRecovery Site
Primary ProductionSite
Standby DatabaseData Guard
1500 miles >
First AmericanOracle Database 10g Benefits
• Higher Availability –transparent node failover• RAC for HA, Data Guard for DR
• Better remote data protection • ASYNC enhancements = less compromise on WAN
• Better protection against logical corruption• Fewer databases, surgically repair vs full point in time
• Less downtime• Faster failover, quicker repair of logical corruptions
Oracle CorporationGlobal Single Instance (GSI)
• A key enabler in Oracle saving $1 billion annually• Consolidation: 1 is the magic number
• Versus 75 separate implementations of Oracle Apps • Versus 100’s of Oracle databases world wide
• Oracle E-Business Suite• 7,000 concurrent users• 5.5TB Oracle database• www.oracle.com
Oracle Global Single InstanceHA/DR Requirements
• HA requirement• Continuous operation regardless of component failure
• DR requirement• Protect against site failure, physical & logical corruption• RPO – 5 minutes of transactions• RTO – database failover in less than 1 hour
• High workload – OLTP system• 8.2MB/sec redo generation at peak, 2.5MB/sec sustained
• WAN, dual OC12• 1,000 miles of separation, 25-35ms RTT network latency
Oracle Global Single InstanceHA/DR Architecture
Primary Database
Data GuardLGWR Asynchronous
redo shipping
Disaster Recovery Site(4) SUN F12Ks
DR domain 8 CPU’s eachDevelopment & Test domain: 28 CPU’s each
GSI Production Site(4) SUN F12Ks36 CPU’s each
Standby Database(4 hour delayed apply)
1,000 miles >
Utilization of Standby Resources
• Four node Standby Cluster• 2 domains: DR, Development & Test• DR domain has sufficient capacity to maintain standby
database and execute failover• At Failover time:
• Failover is executed, standby assumes primary role • Development & Test is stopped• CPU’s are re-allocated to the new production domain• Nodes are upgraded in a rolling fashion with no
application downtime
Delayed Apply – Downtime Avoided
• Human error caused logical corruption on primary• 160,000 row table updated by mistake
• Standby database configured with 4 hour delayed apply
• Instead of 10 hours of downtime, just 30 minutes• Cancel recovery on standby and open read only• Stop the affected application on primary• Export data from standby• Recreate table on primary, import data to primary db after
disabling triggers• Restart application on primary• Restart recovery on standby
Oracle Global Single InstanceOracle Database 10g Feature Adoption
• Flashback Technologies• Flashback Table• Flashback Database
• Data Guard 10g• Real Time Apply• Asynchronous Redo Transport enhancements• Redo Apply performance enhancements
• Benefits• Faster failover, better data protection
Ohio Savings Bank
• Founded in 1899• In Top 20 of all US Mortgage Lenders• Provide mortgage services to independent brokers
nationwide via Web• $13 billion in assets• Reputation for Innovation
• 2002 Web Site of the Year (Mortgage Technology Magazine)
• www.ohiosavings.com
HA/DR Requirements
• 24 x 7 - 365 days/year
• Recovery Point Objective: zero data loss
• Recovery Time Objective: 30 minutes
• Planned maintenance windows Sunday mornings
Ohio Savings BankOracle9i Architecture
Primary Database
Data GuardArchive Log Shipping (ARCH)
3rd party storage based synchronous disk mirroring
for online logs
Remote DR SiteHP N-Class PA-RISCEMC SymmetrixSAN attachedHP-UX v11.0
Primary Production2-node RAC ClusterHP N-Class PA-RISCEMC SymmetrixSAN attachedHP-UX v11.0
15 miles >
Online Mortgage Services
Ohio Savings BankOracle Database 10g Architecture
Primary Database
Data Guard Maximum Availability synchronous redo shipping
Zero Data Loss 15 miles >
Primary Production3-node RAC ClusterHP DL-380, 2 Zeon CPUs/nodeEMC Symmetrix& ClariionSAN attachedRed Hat Linux
Standby Database
Remote DR Site3-node RAC ClusterHP DL-380, 2 Zeon CPUs/nodeEMC Symmetrix& ClariionSAN attachedRed Hat Linux
Customer Call Center
Ohio Savings BankOracle Database 10g Features Deployed
• Automatic Storage Management• Reduces time spent managing storage
• RMAN Flash Recovery Area• Fully automates disk-based backup & recovery
• Oracle Data Guard• Zero Data Loss• Replaces 3rd party remote mirroring• Standby DB also used for daily exports
Ohio Savings BankAutomatic Storage Management
• Automatically spreads database files across all available storage
• Automatic rebalancing of used disk space when disks are added or removed
• Increases I/O distribution beyond disk array striping
• Reduces DBA workload
Ohio Savings Bank, Future PlansGRID – from concept to reality
• Add nodes to the existing RAC 10g cluster
• Manage cluster via a single system view
• Add mortgage database, and potentially the OSB Data Warehouse to same RAC 10g cluster
• Define application workloads as services
• Establish rules to dynamically allocate processing resources to services
• Maximize the utilization of resources while meeting changing business needs
Oracle Disaster Recovery Solution
Includes as Oracle Products:• Oracle Database Enterprise Edition
on both sites
PrimarySite
RAC based
Clients Clients
SecondarySite
Application Servers
Oracle Maximum Availability Architecture
Instance1 Instance2 Instance1 Instance2Data Guard
Application Servers
WAN TrafficManager
Dedicated Network
hbhb
hbhb
Resources
• Maximum Availability Architecture white papers: http://otn.oracle.com/deploy/availability/htdocs/maa.html
• New SQL Apply Best Practices Paper now available!
• HA Portal on OTN: http://otn.oracle.com/deploy/availability
• Data Guard home page on OTN: http://otn.oracle.com/deploy/availability/htdocs/odg_overview.html
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