Overview of High AvailabilityAvaila

Overview of High Availability
Availability is the degree to which an application, service, or functionality is available on demand. For example, an OLTP database used by an online bookseller is available to the extent that it is accessible by customers making purchases. Reliability, recoverability, timely error detection, and continuous operations are the primary characteristics of high availability.
The importance of high availability in a database environment is tied to the cost of downtime, which is the time that a resource is unavailable. Downtime can be categorized as either planned or unplanned. The main challenge when designing a highly available environment is examining all possible causes of downtime and developing a plan to deal with them.
1. High Availability and Unplanned Downtime
Oracle Database provides high availability solutions to prevent, tolerate, and reduce downtime for all types of unplanned failures. Unplanned downtime can be categorized by its causes:
1.1. Site Failures
A site failure occurs when an event causes all or a significant portion of an application to stop processing or slow to an unusable service level. A site failure may affect all processing at a data center, or a subset of applications supported by a data center. Examples include an extended site-wide power or network failure, a natural disaster making a data center inoperable, or a malicious attack on operations or the site.
The simplest form of protection against site failures is to create database backups using RMAN and store them offsite. You can restore the database to another host. However, this technique can be time-consuming, and the backup may not be current. Maintaining one or more standby databases in a Data Guard environment enables you to provide continuous database service if the production site fails.
1.2. Computer Failures
A computer failure outage occurs when the system running the database becomes unavailable because it has shut down or is no longer accessible. Examples of computers failures include hardware and operating system failures.
The following Oracle features protect against or help respond to computer failures:
- Enterprise Grids
In an Oracle Real Applications Cluster (Oracle RAC) environment, Oracle Database runs on two or more systems in a cluster while concurrently accessing a single shared database. A single database system spans multiple hardware systems yet appears to the application as a single database.
- Oracle Data Guard
Data Guard enables you to maintain a copy of a production database, called a standby database, that can reside on a different continent or in the same data center. If the primary database is unavailable because of an outage, then Data Guard can switch any standby database to the primary role, minimizing downtime.
- Oracle Restart
Components in the Oracle Database software stack, including the database instance, listener, and Oracle ASM instance, can restart automatically after a component failure or whenever the database host computer restarts. Oracle Restart ensures that Oracle components are started in the proper order, in accordance with component dependencies.
- Fast Start Fault Recovery
A common cause of unplanned downtime is a system fault or crash. The fast start fault recovery technology in Oracle Database automatically bounds database instance recovery time.
1.3. Storage Failures
A storage failure outage occurs when the storage holding some or all of the database contents becomes unavailable because it has shut down or is no longer accessible. Examples of storage failures include the failure of a disk drive or storage array
- Oracle Automatic Storage Management
- Backup and recovery
1.4. Data Corruption
A data corruption occurs when a hardware, software or network component causes corrupt data to be read or written. For example, a volume manager error causes bad disk read or writes. Data corruptions are rare but can have a catastrophic effect on a database, and therefore a business.
- Lost write protection
- Data block corruption detection
- Data Recovery Advisor
1.5. Human Errors
A human error outage occurs when unintentional or malicious actions are committed that cause data in the database to become logically corrupt or unusable. The service level impact of a human error outage can vary significantly depending on the amount and critical nature of the affected data.
Much research cites human error as the largest cause of downtime. Oracle Database provides powerful tools to help administrators quickly diagnose and recover from these errors. It also includes features that enable end users to recover from problems without administrator involvement.
- Restriction of user access
- Oracle Flashback Technology
- Oracle LogMiner
2. High Availability and Planned Downtime
Planned downtime can be just as disruptive to operations, especially in global enterprises that support users in multiple time zones. In this case, it is important to design a system to minimize planned interruptions such as routine operations, periodic maintenance, and new deployments.

2.1. System and Database Changes
Planned system changes occur when you perform routine and periodic maintenance operations and new deployments, including scheduled changes to the operating environment that occur outside of the organizational data structure in the database. Examples include adding or removing CPUs and cluster nodes (a node is a computer on which a database instance resides), upgrading system hardware or software, and migrating the system platform.
- Dynamic reconfiguration of the database
- Autotuning memory management
- Automated distributions of data files, control files, and online redo log files

2.2. Data Changes
Planned data changes occur when there are changes to the logical structure or physical organization of Oracle Database objects. The primary objective of these changes is to improve performance or manageability. Examples include table redefinition, adding table partitions, and creating or rebuilding indexes.

2.3. Application Changes
Planned application changes may include changes to data, schemas, and programs. The primary objective of these changes is to improve performance, manageability, and functionality. An example is an application upgrade.
- Rolling patch updates
- Rolling release upgrades
- Edition-based redefinition
- DDL with the default WAIT option
- Creation of triggers in a disabled state

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Overview of High Availability Availability is the degree to which an application, service, or the functionality is available upon request. For example, an OLTP database is used by an Online Bookseller available to the extent that it can be accessed by making a purchase. The reliability, recoverability, timely error detection, and continuous operations are the main characteristics of high availability. The importance of high availability in a database environment is tied to the cost of downtime, it is time that a resource is not available. Downtime can be classified as plan or plans. The main challenge when designing an environment that is available to check all the possible causes of downtime and develop a plan to deal with them. 1. high availability and no planned downtime Oracle database provides high availability solutions to prevent, tolerate, and reduce downtime for all types of plan failure. Downtime not plans can be classified according to its cause: 1.1. Site failures A site failure occurs when an event causes all or a significant part of an application to stop processing or slow to an unusable level of service. A ventricular site failure may affect all processing at a data center, or a subset of applications that are supported by a data center. For example, a site-wide expansion power or network loss failure, a natural disaster makes a data center is not working or a malicious attack on the activity or the site. The simplest form of protection against site failure is to create backup the database using RMAN and store them offsite. You can restore the database server. However, this technique can be time consuming, and the backup is not shown in. To maintain one or more standby databases in a data protection environment that enables you to provide service continuity database if the production site fails. 1.2. computer failures A computer failure outage occurs when the system is running the database becomes available, because it has shut down or is no longer accessible. The examples of such computer failure failure of hardware and operating systems. Oracle following features help protect against or respond to computer failure: -Sales net industrial environment in Oracle real application clusters (Oracle RAC), Oracle databases run on two or more systems in a cluster while concurrently accessing the database is shared only. A database system only lasted many hardware systems yet appears to the application as a single database. -Oracle data protection Data Protection allows you to maintain a copy of a production database, called a standby database, which can reside on a different continent or in the same data center. If the database is unavailable because of an outage, then data protection can convert any database Preventive primary role, minimizing downtime. Restarts the oracle The components of the software stack Oracle database, including database instances, hear, and Oracle ASM instances, can restart automatically after a component failure or whenever restart the database server. Restart Oracle Oracle ensures that components are started in the correct order, in accordance with the component dependencies. speedy recovery to start his fault A common cause of downtime is no plan is a system error or accident. Technology speedy recovery started in the Oracle database error automatic data recovery time limit Database example. 1.3. point of failure A failure outage occurs when the storage point of holding some or all of the content database becomes unavailable because it has shut down or is no longer able to access. Example the failure reasons include the failure of a disk drive or array reasonable Manage storage oracle automatic backup and recovery -Why 1.4. Data Corruption A data corruption occurs when a hardware component, software or network failure data is read or written up. For example, a volume manager disk error cause read or write. Data is rare but infections can have serious impacts on a database, and therefore a business. agraphia protect -Data prevent corruption detection adviser -Data recovery 1.5. Human error One human error outage occurs when unintentional or malicious act committed that cause data in the database to become logically corrupted or unusable. Impact level services of a human error outage can vary significantly depending on the amount and the nature of the critical data is affected. Many studies cited human error as the single largest cause of downtime. Oracle Database provides powerful tools to help administrators quickly diagnose and recover from these errors. It also includes features that allow end users to recover from the problem without the involvement of an administrator. -Limited users access Oracle Flashback technology -The -Oracle LogMiner 2. high availability and planned downtime Planning downtime can be disruptive to operations, especially in global enterprises to support users in multiple time zones. In this case, it is important to design a system to minimize planned interruptions as regular operation, routine maintenance, and new deployment process. 2.1. The system and database change plan system changes occur when you perform routine and periodic maintenance operations and new deployments, including changes scheduled to environmental activities happening inside outside of structured data held in databases. For example, adding or removing CPU and cluster nodes (a node is a computer on which a case database resides), upgrade hardware or software, and moving platforms. -Improved the reconfiguration of the database memory -Management Autotuning Automatic distribution of data files, control files and files login online redo 2.2. Data change data plan changes occur when there are changes in structure or physical rational organization objects Oracle database. The main objective of these changes is to improve performance or manageability. For example, the table redefinition, more partition tables, and create or rebuild the index. 2.3. application change application Change plan may include changes to the data, schema and program. The main objective of these changes is to improve performance, manageability and functionality. An example is an application upgrade. -Hot patch update -Hot upgraded version based on the redefinition -The network-cards with the default options waiting -Created factors in disability

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Overview of High Availability
Availability is the degree to which an application, service, or function is available upon request. For example, an OLTP database is used by a seller is available to book online extent that it can be accessed by the customer purchases. The reliability, recoverability, timely error detection, and continuous operations are the main characteristics of high availability.
The importance of High availability in a database environment are tied to the cost of downtime, it is time that a resource is unavailable. Downtime can be classified as planned or external design plan. The main challenge when designing a high-availability environment is checked all possible causes outages and develop a plan to deal with them.
1. High Availability and Unplanned Downtime
Mechanical Oracle database provides high availability solutions to prevent, tolerate, and reduce the time for all kinds of unintended damage. Downtime no plans can be classified according to the cause of it:
1.1. Failure Site
A site failure occurs when an event causes all or a significant part of an application to stop processing or slow to a level of service can not be used. A defeat site can affect all processing at a data center, or a subset of applications that are supported by a data center. For example, a power or network expansion Page wide web, a natural disaster makes a data center is not working, or a malicious attack on the activities or sites.
The simplest form of protection against errors sites is to create the backup database using RMAN and store them offsite. You can restore the database to another host. However, this technique may take time , and the backup may no longer exist. Maintaining one or more standby databases in a Data Guard environment that allows you to provide service continuity database if the production site no.
1.2. Failure computer
A computer outage failure occurs when the system is running the database is unavailable because it has shut down or is no longer accessible. Examples include computer hardware failure and Contacts Operating failures.
The following Oracle features protect against or help cope with computer failure:
- Enterprise Grids
In an Oracle Real Application Cluster (Oracle RAC) environments, Oracle database running on two or more systems in a cluster while concurrently accessing the database is shared only. A database system only lasts hardware system appear to the application as a single database.
- Oracle Data Guard
Data Guard allows you to maintain a copy of a production database, called a standby database, which can reside on a continent different or the same data center. If the database is not available as a power failure, then Data Guard can switch any standby database to the main role, minimizing time dead.
- Oracle Restart
software components in the database Oracle stack, including database instance, hear, and Oracle ASM instance, can restart automatically after a component failure or any Whenever restart the database server. Oracle Restart ensures that Oracle components are started in order of appropriate, consistent with the dependent components.
- Fast Start Fault Recovery
A common cause turn of downtime does not plan a system failure or crash. The fast start fault recovery technology in the database automatically clears the time Oracle database instance recovery.
1.3. Failure storage failure
A storage failure outage occurs when storage holds some or all of the content database is unavailable because it has shut down or is no longer accessible. Examples include the storage error failure of a disk array or storage
- Oracle Automatic Storage Management
- Backup and Restore
1.4. Corruption
may be data errors occur when a hardware, software or network components that may damage data read or write. For example, a volume manager error caused the bad disk read or write. Corruption of data are rare but can have a catastrophic effect on a database, and therefore a business .
- Lost write protection
- Detects corrupt data blocks
- Data Recovery Advisor
1.5. Human error
A human error outage occurs when the act of unintentional or malicious data represent that materials people in the database to become logically corrupted or unusable. The impact of a service-level human error outage can vary significantly depending on the amount and critical nature of Data affected.
Many studies cited human error is the biggest cause of downtime. Oracle Database provides powerful tools to help administrators quickly diagnose and recover from these errors. It also includes features that allow users to recover from problems without administrator involvement.
- Restricting user access
- Oracle Flashback Technologies
- Oracle LogMiner
2 . High Availability and Planned Downtime
planned downtime can be just as disruptive to operations, especially in global enterprises that support users in multiple time zones. In this case, it it is important to design a system to minimize disruption of activities planned as regular, periodic maintenance, and new deployments. 2.1. System database and change plans to change the system happen when you perform regular maintenance activities and periodic and new deployment, including changes expected environmental activities occur outside of the structured data held in databases data. For example, add or remove the CPU and cluster nodes (a node is a computer on which a case database resides), upgrading the system hardware or software, and move the system platform. - Dynamic reconfiguration of the database - Memory management Autotuning - automatic distribution of data files, control files, and redo log files online 2.2. Change data data changes occur when the plan changes the logical structure or physical organization of Oracle database objects. The main objective of these changes is to improve performance or management. The examples include table redefinition, more partition tables, and create or rebuild the index. 2.3. Change the application to change the planned application may include data changes , schema, and the program. The main objective of these changes is to improve the performance, management, and functional. An example is an application upgrade. - Roll the update patches - upgrade released book - Edition-based redefinition - DDL with the default option WAIT - Creation of triggers in disability