Most Organizations setup their disaster recovery environment and hardly able to utilize their disaster recover infrastructure to full capacity.

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Manoj Machiwal, Jade Global Inc.
ABSTRACT
Most Organizations setup their disaster recovery environment and hardly able to utilize their disaster recover infrastructure
to full capacity. In this white paper, you will learn how to setup an active data guard environment and best practices to
setup active data guard environment, which can be utilized as a reporting infrastructure which supports MIS reporting, also
in case of disaster can be used as failback option.
TRADITIONAL DISASTER RECOVERY/HIGH AVAILABILITY SOLUTION
Adding basic fault tolerance to an IT infrastructure is not hard. You can add a few redundant components, and you can claim
fault tolerance, or high availability. If you have some failure in your IT stack, there are redundant components available to
which you can failover. Following this basic principle, some customers have built an HA framework consisting of:
 An N+1 active-passive server clustering model (e.g., clustering integrated with the OS)
 Mirroring of the bits in the storage array to some other remote storage array
 A tape backup product which ensures that periodic backups are taken and stored offsite
 A separate volume management product to ease the management of the underlying storage

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This type of configuration works, but with important limitations, as follows:
 Typically, the solutions mentioned above come from different vendors. Stitching together and managing these
disparate solutions require a non-trivial effort.
 Because the overall architecture is based on disparate point solutions, it is difficult to scale the configuration to
increase throughput. Scaling effectively is critical from an HA standpoint.
 While hardware-centric HA solutions (e.g., mirroring) offer simple data protection methods, their byte-level approach
makes it very difficult to build application-optimized capabilities.
 A related factor is return on investment (ROI) on the HA systems. If a server is configured in a cold-cluster N+1
environment as the failover target, it cannot support production workload, and computing resources are wasted. If a
remote storage array is receiving bits through storage mirroring technology, no applications or databases can be
mounted on that storage array – more waste.
ORACLE DATABASE HIGH AVAILABILITY
Data is one of the most critical business assets of an organization. If this data is not available and/or not protected,
companies may stand to lose millions of dollars in business downtime as well as negative publicity.
Oracle Database have many HA capabilities such as Real Application Clusters (RAC), Data Guard, Automatic Storage
Management (ASM), Flashback, Recovery Manager (RMAN), Online Reorganization, Edition-based Redefinition, etc. are
available as built-in features of the Oracle Database. Along with complementary products such as Oracle Secure Backup and
Oracle Golden Gate, these capabilities work together in an integrated manner to offer the best solution for the Oracle
Database to reduce or eliminate both planned and unplanned downtime.
Oracle also offers the Oracle Maximum Availability Architecture (MAA), which is Oracle's HA best practices blueprint involving
its entire technology stack from applications to storage. Following the MAA guidelines, customers can significantly reduce the
cost and complexity of their HA deployments, while building an HA architecture that is optimized for their Oracle environment.
Following are the key capabilities that comprise Oracle Database's HA solution set.
 Real Application Clusters
 Clusterware
 Data Guard
 GoldenGate
 Streams
 Secure Backup
 Recovery Manager (RMAN)
 Flashback Technologies
 VM
 Cloud Computing
 Cloud Storage
 Cross-Platform Transportable Tablespace
 Edition-Based Redefinition

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 Online Reorganization
ACTIVE DATA GUARD OVERVIEW
Oracle Data Guard is THE solution for Oracle data protection, data availability, and disaster recovery.
Oracle Data Guard provides the management, monitoring, and automation software to create and maintain one or more
standby databases to protect Oracle data from failures, disasters, human error, and data corruptions while providing high
availability for mission critical applications
Data Guard's loosely coupled architecture provides optimal data protection and availability:
 Database changes are transmitted directly from memory, isolating the standby from I/O corruptions that occur at the
primary.
 A standby database uses a different software code-path than the primary – isolating it from firmware and software
errors that impact the primary database.
 Oracle corruption detection insures that data is logically and physically consistent before it is applied to a standby
database.
 Data Guard detects silent corruptions caused by hardware errors (memory, cpu, disk, NIC) and data transfer faults,
and prevents them from impacting the standby database.
 A standby database is used to perform planned maintenance in a rolling fashion, minimizing downtime and
eliminating the risks inherent with introducing change to production environments.

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Traditional Data Guard
Oracle Active Data Guard 11g extends basic Data Guard functionality by allowing read-only access to a physical standby
database while continuously applying changes received from the primary database. This increases performance and return
on investment by offloading ad-hoc queries, Web-based access, reporting, and backups from the primary database while also
providing disaster protection.
Active Data Guard
ENABLING ACTIVE DATA GUARD
The general process of enabling Active Data Guard is as simple as opening the standby database in read-only mode and
starting Redo Apply. This section describes how to enable Active Data Guard on a standby database.
 If the standby instance and redo apply have been cleanly shut down
a. Using SQL*Plus
Start the standby instance in read-only mode.
SQL> startup
Once the database is open, start Redo Apply:
SQL> recover managed standby database disconnect using current logfile;
b. If you are using the Data Guard broker to manage your Data Guard configuration
Start the standby instance in read-only mode.
Connect to the standby instance using DGMGRL and issue the following command:
DGMGRL> startup

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The default state for the standby database is APPLY ON and Redo Apply starts
automatically. If the default has been changed, then start Redo Apply by issuing the
following command:
DGMGRL> EDIT DATABASE ‘RTQ' SET STATE=‘APPLY-ON’
 If the standby database is mounted and redo apply is running using the following steps
Using SQL*Plus
Stop redo apply
SQL> recover managed standby database cancel;
Open the database read only SQL> alter database open read only;
Once the database is open, start redo apply:
SQL> recover managed standby database disconnect using current logfile;
If you are using the Data Guard broker to manage your Data Guard configuration
Stop redo apply using DGMGRL
DGMGRL> EDIT DATABASE ‘RTQ' SET STATE=‘APPLY-OFF’
In SQL*Plus open the database read only
alter database open read only;
Restart redo apply by issuing the following command:
DGMGRL> EDIT DATABASE ‘RTQ' SET STATE=‘APPLY-ON’
Note: In 11gR2, Alter database read only, automatically stops the redo apply
before opening the database and starts redo apply after opening the database
in read only mode.
ACTIVE DATA GUARD COOL FEATURES
• Write Operations to Primary
• This feature helps redirecting updates from an Active Data Guard standby to a remote database, using
database link. This feature is very useful for applications which are doing mostly read operations except a very
few write operations. These write operations can be redirected to Primary database using database link.
• Automatic Repair of Block Corruption
• When Oracle detects corrupt blocks at the primary database, it will repair online by copying the good
version from an active standby database (and vice versa)
MAINTENANCE/MENTORING TIPS
• Confirming Active Data Guard is Enabled

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SQL> SELECT OPEN_MODE FROM V$DATABASE;
OPEN_MODE
---------------------
READ ONLY WITH APPLY
• Monitor the Apply Lag
SELECT name, value, datum_time, time_computed FROM V$DATAGUARD_STATS WHERE
name like 'apply lag';
SELECT * FROM V$STANDBY_EVENT_HISTOGRAM
WHERE NAME = 'apply lag' AND COUNT > 0;
CUSTOMER CASE STUDY
a. Customer Background
• Industry
– Solar Manufacturing
• Technical foot Print
– 11gR2
– 2 Node RAC
– Exadata Machine
• Application
– Factory Operations
– MES Reporting
b. Customer Challenges
• Manufacturing Operations and Reporting Operations running on Same database, which creates the resource
hogging issues while running reports and manufacturing operations have significant impact.
• No High Availability Architecture
• Exadata Patching was challenge as system cannot be brought down and there is no HA environment
c. Existing Infrastructure

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d. Proposed Infrastructure
e. Lessons Learned
 Failover site was not tuned for Factory operations so Factory operations were having performance issues
while switching over to standby site for doing patching on Exadata Machine.

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 Lot of Rework need to be planned as reporting queries were originally optimized in terms of Exadata
Machine and they have to be reworked and tuned to work on Active Standby Environment.
 Use of RAT Capture and RAT Replay should have been done effectively to measure performance of active
standby during actual rollover and Switchover for exadata patching, this would have identified many issues in
advance and corrective actions could have been applied in advance.
About the Author
Manoj Machiwal is a Consulting Director at Jade Global. He has over 12 years of experience in Oracle DBA and Oracle
Apps DBA. Manoj is a specialist in Upgrades, Migrations, High Availability and Performance, Datawarehouse architecting
and Proactive Monitoring. Manoj has worked for some major names in the industry including Solyndra, Orbotech, Gallo
Wineries, Silicon Storage Technology (SST),Telegent Systems, Riverbed Technology, Cisco Systems and Merrill Lynch. He
is also an Oracle Certified Professional DBA .Manoj can be reached at manoj.machiwal@jadeglobal.com and on +1-408-
899-7217.