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HP IT-Symposium 2006 This presentation is for informational purposes only and may not be incorporated into a contract or agreement. This document is for informational purposes. It is not a commitment to deliver any material, code, or

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“This presentation is for informational purposes only and may not be incorporated into a contract or agreement.”

This document is for informational purposes. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described in this document remains at the sole discretion of Oracle. This document in any form, software or printed matter, contains proprietary information that is the exclusive property of Oracle. This document and information contained herein may not be disclosed, copied, reproduced or distributed to anyone outside Oracle without prior written consent of Oracle. This document is not part of your license agreement nor can it be incorporated into any contractual agreement with Oracle or its subsidiaries or affiliates.

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Automatic Failover across sites with Data Guard Fast-Start Failover

DECUS, Duesseldorf 2006

Larry M. Carpenter Principal Product Manager High Availability & Disaster Recovery Oracle USA

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Agenda

  • A quick look at Data Guard
  • How do users perform Failover today?
  • Fast-Start Failover – An Overview
  • Fast-Start Failover – The Details
  • Client Failover
  • User Experiences

A quick look at Data Guard

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What is Oracle Data Guard?

  • Oracle’s Disaster Recovery solution for Oracle.
  • A Feature of Oracle Database Enterprise Edition
  • Automates the creation and maintenance of one
  • r more transactionally consistent Standby

databases.

  • Provides comprehensive role management.
  • Role transitions
  • Standby to Primary and back to Standby
  • For planned and unplanned outages

A Data Guard Configuration

  • Managed as a single configuration
  • Primary and standby databases can be Real Application Clusters
  • r single-instance Oracle
  • Up to nine standby databases supported in a single configuration

Primary Database Standby Database

Standby Site A Standby Site B Primary Site

Standby Database

Broker

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How do users perform Failover today? Failover Implications

  • Faster is better - Downtime is bad
  • If manual intervention is required, the time it

takes to notify administrative staff can be lengthy

  • Reliability is a must-have
  • Correct procedure for failover must be followed to

meet data loss (recovery point) objective

  • Simplicity is preferred
  • Determining if failure condition warrants failover

adds time & complexity to the failover process

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Best Practice Add Standby Redo Logs

  • A separate pool of log file groups on a

standby site

  • Used just like the online redo logs on a primary
  • Requires local archiving on the standby database
  • Requires same size and number of Primary

database online redo logs but more is better

  • Cannot be assigned to a thread in 9i
  • Are required for Zero Data loss configurations as
  • f Oracle Database10g Release 1.

SRL Architecture

Redo from primary database ARCH Standby Redo Logs Archived Redo Logs Physical & Logical standby databases RFS LGWR ARCH RFS

New!

10 g 10 g

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Benefits

  • Better Performance
  • Standby redo logs are pre-allocated files
  • Can reside on raw devices
  • Better Protection
  • Can have multiple members
  • If primary database failure occurs, redo data

written to standby redo logs can be fully recovered.

Failover

  • Failover needed when switchover not possible
  • i.e. The primary is gone!
  • Same basic steps as switchover but some

processing might be done manually

  • Remember!
  • Don’t plan for DR by expecting to be able to

return to the Primary and ‘get’ something.

  • You won’t be able to ‘get’ anything.
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Choose a Standby

  • Choose a standby site with the most up to date redo

information

  • If Primary was ‘protected’ then one site must have the

‘latest’ redo information in its Standby On-line Redo logs

  • Archive Log file ‘GAPs’ at this site must be resolved from

the other standby sites

  • Choose a Physical and other standby databases will

come along if possible.

  • Choose a Logical and none of the other standby

databases can come along

Physical Standby Failover

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Failover to a Physical Standby

Primary Database Physical Standby Database

ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH; ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;

1 2 3

RESTART DATABASE

Step 1 Improvements

  • In Oracle Database10g Release 2
  • New FORCE keyword
  • RECOVER MANAGED STANDBY DATABASE

FINISH FORCE;

  • The new FORCE option stops active RFS

processes on the target standby database so the failover will proceed immediately, without waiting for network connections to time out, once logs have been applied.

  • SQLNET.EXPIRE_TIME no longer necessary.

10.2.0.1

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Step 3 Improvements

  • In Oracle Database10g Release 2
  • No longer necessary to restart the Standby for it

to become the Primary, just do an:

  • ALTER DATABASE OPEN;
  • Requires that the standby was not opened read
  • nly since it was last started.
  • Speeds up failover time considerably.

10.2.0.1

Failover to a Physical Standby

Primary Database Physical Standby Database

ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH FORCE; ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;

1 2 3

ALTER DATABASE OPEN;

10.2.0.1

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Logical Standby Failover Failover to a Logical Standby

Primary Database Logical Standby Database

ALTER DATABASE STOP LOGICAL STANDBY APPLY; ALTER DATABASE START LOGICAL STANDBY APPLY FINISH;

1 2

ALTER DATABASE ACTIVATE LOGICAL STANDBY DATABASE;

4

ALTER DATABASE STOP LOGICAL STANDBY APPLY;

3

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Reduced Steps

  • In Oracle Database10g Release 2
  • Apply finish and failover now in one command.
  • No longer necessary to start or stop the Apply.

10.2.0.1

Failover to a Logical Standby

Primary Database Logical Standby Database

ALTER DATABASE ACTIVATE LOGICAL STANDBY DATABASE FINISH APPLY;

1

10.2.0.1

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Using the Data Guard Broker One Step always!

  • Login to DGMGRL by connecting to any

surviving database in the configuration

  • And execute the failover!
  • DGMGRL> FAILOVER TO <database>;
  • You still need to decide which standby to use

as the target of the failover!

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What about Grid Control?

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Fast-Start Failover

Eliminate the Manual Steps!

Remember the Requirements?

  • Faster is better - Downtime is bad?
  • Site failover time measured in seconds
  • Not minutes
  • Failover is automatic, no manual intervention
  • Reliability is a must-have?
  • Eliminates human error
  • Simplicity is preferred?
  • Automatically determines if failover criteria met
  • Original primary database is automatically

reinstated as a new standby database.

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Fast-Start Failover Architecture

  • Primary Database
  • Target Standby

Database

  • Observer Process

Standby Site Primary Site Observer

database database

Fast-Start Failover

The Details

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Fast-Start Failover Requirements

  • Primary and Standby are managed by the

Data Guard Broker

  • Primary database must be in Maximum

Availability mode

  • Primary and standby must have Flashback

Database enabled

  • Observer host must have DGMGRL utility

installed and must have Oracle Net connectivity to both the primary and standby

Setting it up using Grid Control

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Using the Broker Directly

DGMGRL command line interface

Set the Target and Threshold

  • Configure
  • “FastStartFailoverTarget” is the “DB_UNIQUE_NAME” of the

target standby database. Using DGMGRL;

  • DGMGRL> EDIT DATABASE 'North_Sales‘

SET PROPERTY FastStartFailoverTarget =‘DR_Sales’;

  • “FastStartFailoverThreshold” is the Number of seconds

Observer attempts to reconnect to the primary database before initiating fast-start failover

  • DGMGRL> EDIT CONFIGURATION

SET PROPERTY FastStartFailoverThreshold = 45;

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Enable and Startup

  • Enable
  • Can be done before or after the Observer
  • DGMGRL> ENABLE FAST_START FAILOVER;
  • Start
  • Log in to the Observer host
  • DGMGRL> START OBSERVER;
  • Control is not returned to the user until the
  • bserver is stopped
  • Specify the -logfile parameter on the

command line so that output generated while acting as the observer is not lost.

Post Failover

  • Reinstate After Failover
  • Auto reinstatement of old primary as a new

standby will happen when the original Primary database is available again.

  • Can also be performed manually
  • DGMGRL> REINSTATE DATABASE <database>;
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How does it work? Fast-Start Failover

Standby Site Primary Site

Observer

1. Data Guard in steady state – transmitting redo 2. Observer monitoring state of the configuration

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Fast-Start Failover

Standby Site Primary Site

Observer

3. Disaster strikes the primary – connections lost

Fast-Start Failover

Standby Site Primary Site

Observer

4. Observer <=> primary connection times out (timeout threshold configurable) 5. Observer asks target standby if it is ready to fail over 6. Observer begins Fast-Start Failover

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Fast-Start Failover

Observer

Primary Site

7. Target standby automatically becomes new primary

Fast-Start Failover

Observer

Standby Site Primary Site

8. After old primary is repaired, Observer re-establishes connection 9. Observer automatically reinstates old primary to be a new standby

  • 10. Redo transmission starts from new primary to new standby
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When is a Fast-Start Failover Triggered?

  • Primary Site Failure
  • Primary Database Conditions:
  • Instance Failure
  • Last surviving instance if RAC
  • Shutdown abort of the last available instance
  • Datafiles taken offline due to I/O errors
  • Threshold ignored when performing a failover

due to offline datafiles

When is a Fast-Start Failover Triggered?

  • Network Related Conditions:
  • Failover occurs only if link between primary and
  • bserver as well as primary and standby are

down

  • Requires a connection between Observer and

standby to enable the Observer to confirm that the configuration is in a synchronized state

  • By ensuring that at least two fast-start failover

partners are present, conditions such as split- brain scenarios are avoided

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Fast-Start Failover Monitoring Fast-Start Failover Monitoring

  • Monitor current state of configuration via

FS_FAILOVER_STATUS column of V$DATABASE

  • SYNCHRONIZED – Primary and Standby are in sync
  • UNSYNCHRONIZED – Standby does not have all of

the primary database redo

  • Monitor the Observer via the

FS_FAILOVER_OBSERVER_PRESENT column of the V$DATABASE view

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Reinstatement after Fast-Start Failover

  • Any attempt to start old primary will stop at the

mount state thus preventing split brain

  • Once Observer sees the old primary is at the

mount state, reinstatement is begun

  • The old primary is automatically reinstated as

the new standby using flashback database

  • Once reinstated and synchronized then a

switchover can occur if desired – returning all systems to their original roles

Best Practices – Primary Database

  • Maximum Availability Protection Mode
  • Redo Transport: LGWR SYNC AFFIRM
  • Synchronous Redo Shipping . . . but
  • Primary is not affected by network or standby outages
  • Set net_timeout parameter to override TCP timeout
  • Configure Flashback Database
  • Set DB_FLASBACK_RETENTION_TARGET = 10 minutes

Note: If Flashback Database serves additional function of protection against user error & corruption, then an extended flashback retention period should be set for an amount of time required to achieve these goals

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Best Practices – Network Transport

  • Tune OS & network parameters
  • Set SDU=32K
  • Tune network parameters that affect network

buffer sizes and queue lengths

  • Ensure sufficient network bandwidth for

maximum database redo rate + other activities

Refer to Primary Site and Network Configuration Best Practices

http://www.oracle.com/technology/deploy/availability/pdf/MAA_DG_NetBestPrac.pdf

Impact of Network Tuning

Impact of Network Tuning

937 10.8 200 400 600 800 1000 Tuned Default Network throughput Mbits/sec

Oracle MAA Test Result

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Best Practices – Standby Database

  • Use Standby Redo Logs
  • Use Real-time Apply
  • Configure Flashback Database
  • Set DB_FLASBACK_RETENTION_TARGET = 10 (minutes)
  • Optimize Apply Performance using MAA Best

Practices for:

  • Redo Apply (physical standby):

Data Guard Redo Apply and Media Recovery

  • SQL Apply (logical standby):

Oracle Database 10g Data Guard SQL Apply

  • MAA Home Page on OTN:

http://www.oracle.com/technology/deploy/availability/htdocs/maa.htm

Best Practices – Observer

  • Install in a separate location from Primary &

Standby data centers

  • Do not locate the Observer at or near the primary site
  • Proximity to the standby site is preferred, but far

enough away to be isolated from events that typically impact the standby site

  • Oracle Client Administrator install is all that is required

for Observer install

  • If using Enterprise Manger, also install the Enterprise

Manager Agent

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Best Practices – Setting FastStartFailoverThreshold

  • Failover occurs when observer and standby

lose contact for specified time (seconds)

  • Recommended settings:
  • Single Instance primary with low latency reliable

network = 10 – 15 seconds

  • Single Instance primary with high latency network
  • ver WAN = 30 – 45 seconds
  • RAC primary = (misscount+reconfiguration time)

+ 20-40 seconds

Best Practices – Multiple Standbys

  • Ensure data protection at all times by maintaining a

2nd Data Guard standby at a remote location

  • When regulatory & business requirements mandate

that data be protected at all times

  • At failover time, the remote standby automatically

becomes a standby for the new primary

  • New primary must have begun as a physical standby
  • Configure the remote standby for Maximum

Performance

  • Eliminates overhead of WAN network latency
  • Recommended redo transport is LGWR ASYNC
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Best Practices – HA & DR

  • Use RAC & Data Guard Together
  • The best possible combination of HA & DR
  • Scalable, flexible, secure
  • Foundation for MAA

Client Failover

Oracle Database 10g Release 1 vs Oracle Database 10g Release 2

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Oracle Database 10g Release 1 Client Failover

Standby Site Primary Site

  • 1. Primary site failure
  • 2. Both FAN ONS (JDBC) and OCI clients wait for TCP timeout

JDBC/OCI Clients

Oracle Database 10g Release 1 Client Failover

New Primary Site Failed Primary Site

  • 3. Data Guard manual failover is executed, standby database transitions to primary role
  • 4. FAN ONS (JDBC) and OCI clients are NOT notified of new primary cluster
  • 5. Clients are redirected manually using TAF or some other mechanism
  • 6. Old primary database is rebuilt from a new backup

JDBC/OCI Clients

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A Sample Hardware Solution

Cisco Distributed Directory

Data Guard

Internet Internet

Cisco Local Directory Cisco Local Directory Application Servers Application Servers

RAC RAC

Primary Standby

A DNS Solution

Primary Standby

Data Guard

Internet Internet

Application Servers Application Servers

RAC RAC

DNS Server

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A TNS Method

  • Use the ‘service_name’ parameter to have

whomever is the Primary defined with the name the applications look for.

  • Works with Dynamic registering of the database

with the listener when the database is mounted.

  • Requires that the parameter be changed

accordingly.

  • Requires a 2nd tnsnames entry for Data Guard

transport services.

On the Primary System

  • Configure the listener and start it.
  • LISTENER.ORA
  • Status

LISTENER = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = Primary)(PORT = 1521)) ) Listener Parameter File /private2/oracle/OraHome/network/admin/listener.ora Listening Endpoints Summary... (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=Primary)(PORT=1521))) Services Summary... Service “payroll.us.oracle.com" has 1 instance(s). Service “payrollDR.us.oracle.com" has 1 instance(s). The command completed successfully

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On the Standby System

  • Configure the listener and start it.
  • LISTENER.ORA
  • Status

LISTENER = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = Standby)(PORT = 1521)) ) Listener Parameter File /private2/oracle/OraHome92/network/admin/listener.ora Listening Endpoints Summary... (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=Standby)(PORT=1521))) Services Summary... Service “payrollDR.us.oracle.com" has 1 instance(s). The command completed successfully

Primary System TNS

  • Primary tnsnames.ora

PAYROLLDR = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = Standby.us.oracle.com)(PORT = 1521)) ) (CONNECT_DATA = (SERVICE_NAME = payrollDR.us.oracle.com) ) ) PAYROLL = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = Standby.us.oracle.com)(PORT = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = Primary.us.oracle.com)(PORT = 1521)) ) (CONNECT_DATA = (SERVICE_NAME = payroll.us.oracle.com) ) )

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Standby System TNS

  • Standby tnsnames.ora

PAYROLLDR = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = Primary.us.oracle.com)(PORT = 1521)) ) (CONNECT_DATA = (SERVICE_NAME = payrollDR.us.oracle.com) ) ) PAYROLL = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = Standby.us.oracle.com)(PORT = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = Primary.us.oracle.com)(PORT = 1521)) ) (CONNECT_DATA = (SERVICE_NAME = payroll.us.oracle.com) ) )

After Switchover or Failover

  • Reset the service_names parameter
  • New Primary (The ‘Old Standby’)
  • New standby (The Old Primary)
  • The LOG_ARCHIVE_DEST definitions point

to each other using payrollDR

  • The application client systems only have the

Payroll definition so they try system 1 first then system 2.

ALTER SYSTEM SET SERVICE_NAMES=‘payroll,payrollDR’; ALTER SYSTEM SET SERVICE_NAMES=‘payrollDR’;

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A TNS setup

Data Guard

Users Users

DBLINKS

Trading Operational Data Store

Primary Site Secondary Site

What about RAC?

  • Multiple addresses are required for the

Primary RAC nodes to facilitate node failover

  • Cannot really have multiple Primary RAC

hosts and then Standby RAC hosts in the same connect string.

  • Would require too many connect timeouts to get

to the standby

  • Need a better more proactive method
  • Let’s talk about Oracle Database10g Release 2
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Oracle Database 10g Release 2 Improved Client Failover

New Primary Site Failed Primary Site 1. Observer detects failure, executes database failover when threshold is exceeded 2. DB_ROLE_CHANGE trigger fires: enables primary service, updates Oracle Net alias to point to new primary host, restarts JDBC mid-tier clients, calls any other application or pre- failover steps User writes the trigger code 3. DB_DOWN event is sent to FAN OCI clients 4. Both FAN ONS (JDBC) and OCI clients drop connections and re-attach to the new primary 5. Upon restart, the old primary database is reinstated automatically by Fast-Start Failover

JDBC/OCI Clients

Observer

Client Failover Components

  • Connect Time Failover
  • Redirects failed connection requests to a

secondary listener

  • Transparent Application Failover (TAF)
  • Client applications automatically reconnect to a

database if the original connection fails.

  • Fast Application Notification (FAN)
  • Provides quick notification when a resource (an

instance, service, node, or database) fails.

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Client Failover Components

  • Fast Connection Failover (FCF)
  • Provides fast failover of database connections by

allowing you to configure FAN-integrated clients to automatically subscribe to FAN HA events.

  • DB_ROLE_CHANGE system event
  • Fired when the primary database is first opened

after a Data Guard role transition has occurred.

  • DB_DOWN Event
  • Fired by the Broker after a failover

DB_ROLE_CHANGE Event

  • New DB_ROLE_CHANGE system event fires.
  • A Trigger written around DB_ROLE_CHANGE

event can automatically:

  • Enable primary service name
  • Modify LDAP or other naming methods
  • Restart JDBC mid-tier clients
  • Start user applications
  • Happens at all role changes.
  • All details with examples are described in the

MAA Best Practices paper published on OTN

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A Sample Trigger

SQL> CREATE OR REPLACE TRIGGER set_rc_svc AFTER DB_ROLE_CHANGE ON DATABASE DECLARE role VARCHAR(30); BEGIN SELECT DATABASE_ROLE INTO role FROM V$DATABASE; IF role = 'PRIMARY' THEN DBMS_SERVICE.START_SERVICE(‘payroll'); begin dbms_scheduler.create_job( job_name=>'change_ldap', job_type=>'executable', job_action=>'/u01/oracle/10.2.0/bin/change_ldap.sh', enabled=>TRUE); end; begin dbms_scheduler.create_job( job_name=>'publish_events', job_type=>'executable', job_action=>'/u01/oracle/10.2.0/bin/cfo.sh', enabled=>TRUE ); end; ELSE DBMS_SERVICE.STOP_SERVICE(‘payroll'); END IF; END;

Data Guard Broker Client Redirection

  • New DB_DOWN event is posted after the new

primary is open

  • Event notifies FAN OCI clients that the old

primary is down

  • Clients reconnect to the new primary/service
  • Done via AQ notifications
  • Occurs only during a Broker Failover
  • A Fast-Start Failover
  • Manual “Failover to <database>” command
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Fast-Start Failover How Available? How Fast? How Simple? How Reliable?

Amazon.com Fannie Mae Thomson Legal & Regulatory Airbus Deutschland GmbH

How Available? - Amazon.com

The capability of fast, guaranteed zero-data-loss failover with Fast-Start Failover in Oracle Data Guard takes the availability of an Oracle database platform to new levels. Our initial tests running Oracle Database 10g Release 2, show that Fast- Start Failover offers a magnitude of improvement in availability.

Rajesh Sheth Manager, Database Engineering Amazon.com

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How Fast? - Fannie Mae

Fast-start Failover takes the DBA off the critical

  • path. Database failover is automatic. Data Guard

can now address recovery time objectives measured in seconds.

Ranjit Singh Veen Manager, Enterprise Systems Management Fannie Mae

How Simple? - Thomson Legal & Regulatory

Fast-start failover testing has shown great potential. The original primary database can be reinstated as a new standby in less than 5 minutes once the initial failure has been corrected.

Thomson Legal & Regulatory

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How Reliable? - Airbus

Failover executed automatically without manual intervention in less than a minute. This was much faster than a cold failover using third party cluster technology. With Data Guard, Airbus can achieve continuous data protection and high levels of availability using a standard feature of the Oracle Database.

Werner Kawollek Application Management Operations Airbus Deutschland GmbH

Q U E S T I O N S Q U E S T I O N S A N S W E R S A N S W E R S

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