Oracle DBA Guide.
Oracle Data guard & High Availability
Oracle Data guard is one of the High availability solution for oracle.
What is high availability.
As an oracle database administrator, it is your responsibility to keep the database up and running with optimal performance. When database is not performing with the normal speed, it is considered again as non-available. In other words, any kind of business interruption is considered to be non-availability.
High availability is a term referred to availability of database around the clock, with expected normal performance.
There are number of related issues while addressing the High availability (HA) solution and some of the critical components to consider are
- Disasters
- Performance
- Availability
- Manageability
High availability (HA) for Disaster.
When there is an unexpected disaster which could blow away the entire database, in order to bring the database back up and running we need to have a failover system in case there is a disaster at primary database site. Having an additional failover system requires additional technology in place to recover the database within reasonable timeframe, in case of complete system loss. Oracle data guard is oracle provided HA solution to handle this kind of unexpected disaster and also recover the system within reasonable timeframe (possibly within few minutes).
High availability (HA) for Performance.
When you experience performance degradation in the database due to capacity issues, you may have scale up the system. Similarly whenever you wish to down size the capacity for whatever reason, you may have to scale down the system. In case of HA Database system, you should be able to scale up or scale down the system without interrupting the business and without compromising the availability of the database. Oracle Real application cluster is the Oracle provided HA solution for Configuring and managing the performance and capacity related issue with databases.
High availability (HA) for Availability
Database availability issue needs to be addressed and taken care based on whether availability issue is to address the capacity, performance or Disaster.
High availability (HA) for Manageability.
Well! When it comes to deploying new technology, any organization needs to weight the benefits of availability against management costs. All High availability solutions (HA) solutions do cost money with respect to new software licence, ongoing managing cost, training the staff in new technology ete etc.
Whatever the requirement is Oracle data guard and oracle Real application cluster combined together provide complete High availability solution.
What is Oracle Data Guard ?
Oracle data guard is a high availability (HA) solution which consists of comprehensive set of services that create, manage, maintain and monitor one or more standby databases depending on requirement, to enable production Oracle databases to survive disasters and data corruptions.
All Standby databases are transactionally consistent copies of Production with very minimum lag. The main fuction of these standby databases is to play the role of primary production database in case of any disaster to production database and it becomes unavailable. In attempt to switching the role between Primary Production and Standby, downtime associated with outage window needs to be very minimum.
Oracle Data guard Configuration
Simple oracle data guard setup would have one primary database and one standby database. However you could have multiple standby databases operating in different phisical locations for the same single primary production database.
Primary production database and standby database is connected by Oracle Net and may be dispersed geographically even several miles apart.
Technically primary production database and standby databases are managed using SQL command-line interfaces or the Data Guard broker interfaces that has a command-line interface (DGMGRL) and a graphical user interface that is integrated in Oracle Enterprise Manager.
What is Primary database in Orcale Data Guard ?
Primary database in Oracle Data guard refres to the main production database that is accessed by most of your applications. This database performas the primary role. The primary database can be either a single-instance Oracle database or an Oracle Real Application Clusters database.
What is Standby Database in Orcale Data Guard ?
In oracle data guard , a standby database is a transactionally consistent copy of the primary production database.
Transactional consistency with standby database is achived by transmitting redo data from the primary database and then applying the redo to the standby database. At any given point is time data in standby database is in sync with primary database except few online redo logs. Just like primary database, standby database can be either a single-instance Oracle database or an Oracle Real Application Clusters database.
Standby database can be configured as logical standby or Physical standby depending on the purpose of standby database.
What is Physical standby database in oracle data guard ?
- Physical standby is basically an identical copy of primary database.
- It’s functionality is to provide disaster recovery solution to the primary database.
- With respect to database structure, schema and object it is identical to primary database.
- Physical standby database is a synchronized copy of primary database by constantly applying the online redo logs from primary database.
What is Logical standby database in oracle data guard ?
- As long as functionality is concerned Logical standby is configured for reporting purposes.
- Logical standby contains same physical structure and logical information as physical standby.
- In case of logical standby, synchronization between physical database and standby is achieved by by transforming the data in the redo received from the primary database into SQL statements and then executing the SQL statements on the standby database.
- Though reporting is main functionality of logical standby, it can also be used for disaster recovery requirements.
- You can upgrade oracle software and patch sets with almost zero downtime by using logical standby.
- So basically logical standby can be used for data protection, reporting, and database upgrades concurrently.
Oracle Database Data guard DBA
As an Oracle DBA if you happen to administer and manage Oracle Data guard for Disaster Recovery or Reporting purpose, you may have to be conversant with following topics
- Create a physical standby database and Logical Standby Database.
- Data Guard Broker configuration and overview.
- Monitoring the Data Guard Configuration and Managing the Data Guard Configuration.
- Configure and Enable fast-start failover.
- Identify the factors that affect planned and unplanned downtime.
- Performing Role Transitions between primary and standby databases.
- Backup and Recovery Considerations in an Oracle Data Guard Configuration.
- Upgrading Databases in a Data Guard Configuration.
If you are looking for any Oracle Data guard training Click Oracle Data guard Training
For remaining skill sets and training requirement for Oracle DBA click on Successful Oracle DBA training needs.
The Practical Handbook on Oracle Real Application Cluster for Oracle DBA’s.
The “Oracle Real Application Cluster Field DBA Admin Handbook” is a practical guide for Oracle DBA’s who manage and administer the Oracle Real Application Cluster High availability solution.
This book provides practical steps to administer Oracle Real Application Cluster (RAC). It’s like a field guide rather than an in depth manual. It’s written for the DBA’s to handle the day to day challenges faced by DBA’s managing RAC on the job.
Click Oracle Real Application Cluster Field DBA Admin Handbook. for more details.
The Practical guide to Unix Commands and Tips for Oracle DBA’s and Developers.
The “Unix Handbook for Oracle DBA” is a practical guide for Oracle DBA’s and Developers working on Unix. It has the unix commands, tips and short scripts to help you find the most needed help on the job. It’s from my collection for over 15 years of practical usage of these tips and techniques as a Database Specialist on Unix.
Click Unix handbook for Oracle DBA. for more details.
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