Oracle Data Guard ensures high availability, data protection, and disaster recovery for enterprise data. Data Guard provides a comprehensive set of services that create, maintain, manage, and monitor one or more standby databases to enable Oracle databases to survive outages of any kind, including natural disasters and data corruptions. A Data Guard standby database is an exact replica of the production database and thus can be transparently utilized in combination with traditional backup, restoration, flashback, and cluster techniques to provide the highest possible level of data protection and data availability. Data Guard is included in Oracle Enterprise Edition.

A Data Guard configuration consists of one primary database and one or more standby databases. A primary database can be either a single-instance Oracle database or an Oracle RAC database. Similar to a primary database, a standby database can be either a single-instance Oracle database or an Oracle RAC database. Using a backup copy of the primary database, you can create up to 30 standby databases that receive redo directly from the primary database. Optionally you can use a cascaded standby to create Data Guard configurations where the primary transmits redo to a single remote destination, and that destination forwards redo to multiple standby databases. This enables a primary database to efficiently synchronize many more than 30 standby databases if desired.

There are several types of standby databases. Data Guard physical standby database is the MAA best practice for data protection and disaster recovery and is the most common type of standby database used. A physical standby database uses Redo Apply (an extension of Oracle media recovery) to maintain an exact, physical replica of the production database. When configured using MAA best practices, Redo Apply uses multiple Oracle-aware validation checks to prevent corruptions that can impact a primary database from impacting the standby. Other types of Data Guard standby databases include: snapshot standby (a standby open read/write for test or other purposes) and logical standby (used to reduce planned downtime).

Topics:

• Oracle Active Data Guard
  
• Data Guard Advantages Over Traditional Solutions
  
• Data Guard and Planned Maintenance
  

Unlike replication solutions from other vendors, Oracle GoldenGate is more closely integrated with Oracle Database while also providing an open, modular architecture ideal for replication across heterogeneous database management systems. This combination of attributes eliminates compromise, making Oracle GoldenGate the preferred replication solution for addressing requirements that span Oracle Database and non-Oracle Database environments.

A typical environment includes a capture, pump, and delivery process. Each of these processes can run on most of the popular operating systems and databases, including Oracle Database and non-Oracle databases. All or a portion of the data can be replicated, and the data within any of these processes can be manipulated for not only heterogeneous environments but also different database schemas, table names, or table structures. Oracle GoldenGate also supports bidirectional replication with preconfigured conflict detection and resolution handlers to aid in resolving data conflicts.

Topics:

• Oracle GoldenGate 12c
  
• Oracle GoldenGate and Maximum Availability Architecture
  Oracle GoldenGate logical replication enables all databases in an Oracle GoldenGate configuration, both source and target databases, to be open read-write.
• Oracle GoldenGate with Oracle Real Application Clusters
  When using Oracle Real Application Clusters (RAC), Oracle GoldenGate can be configured so that it seamlessly moves between Oracle RAC nodes in the event of database instance failure or during applicable maintenance operations.

While Oracle Active Data Guard and Oracle GoldenGate are each capable of maintaining a synchronized copy of an Oracle database, each has unique characteristics that result in high availability architectures that can use one technology or the other, or both at the same time, depending upon requirements. Examples of MAA Best Practice guidelines for use cases relevant to Oracle Database 12c are as follows:

Topics:

• When to Use Oracle Active Data Guard
  
• When to Use Oracle GoldenGate
  
• When to Use Oracle Active Data Guard and Oracle GoldenGate Together
  

Recovery Manager (RMAN) provides a comprehensive foundation for efficiently backing up and recovering the database. RMAN eliminates operational complexity while providing superior performance and availability of the database.

RMAN determines the most efficient method of executing the requested backup, restoration, or recovery operation and then submits these operations to the Oracle Database server for processing. RMAN and the server automatically identify modifications to the structure of the database and dynamically adjust the required operation to adapt to the changes.

RMAN is the standard interface to backup and restore from Recovery Appliance, local disk (ZFS storage), tape, and cloud object store.

RMAN provides the following benefits:

• Support for Oracle Sharding - RMAN support for every independent database (shard) (new in Oracle Database 12c Release 2)

• Enhancement for Sparse Databases - allows backup and restore to operate on SPARSE backup sets and or image copies (new in Oracle Database 12c Release 2)

• Over the Network Standby Database repair of NONLOGGED operation - new syntax for validation and repair on Standby - VALIDATE/RECOVER .. NONLOGGED BLOCK; (new in Oracle Database 12c Release 2)

• RMAN DUPLICATE feature enhanced to support creation of Far Sync from Primary and backup (new in Oracle Database 12c Release 2)

• RMAN DUPLICATE Using Encrypted Backups - RMAN enhanced support non Auto-login wallet based encrypted backups with a new SET command - enables interrupt-free cloning (new in Oracle Database 12c Release 2)

• Support for cross-platform backup and restore over the network (new in Oracle Database 12c Release 2)

• Network-enabled restoration allows the RESTORE operations to copy data files directly from one database to another over the network

• Simplified table restoration with the RECOVER TABLE command

• Support for Oracle Multitenant, including backup and recovery of individual pluggable databases

• Support for cross-platform Oracle Multitenant, including backup and recovery of individual PDBs (new in Oracle Database 12c Release 2)

• Automatic channel failover on backup and restore operations

• Automatic failover to a previous backup when the restore operation discovers a missing or corrupt backup

• Automatic creation of new database files and temporary files during recovery

• Automatic recovery through a previous point-in-time recovery—recovery through reset logs

• Block media recovery, which enables the data file to remain online while fixing the block corruption

• Fast incremental backups using block change tracking

• Fast backup and restore operations with intrafile and interfile parallelism

• Enhanced security with a virtual private recovery catalog

• Merger of incremental backups into image copies, providing up-to-date recoverability

• Optimized backup and restoration of required files only

• Retention policy to ensure that relevant backups are retained

• Ability to resume backup and restore operations in case of failure

• Automatic backup of the control file and the server parameter file, ensuring that backup metadata is available in times of database structural changes and media failure and disasters

• Easily reinstantiate a new database from an existing backup or directly from the production database (thus eliminating staging areas) using the DUPLICATE command.

Oracle Secure Backup is a centralized backup management solution supporting disk and tape targets, providing heterogeneous data protection in distributed UNIX, Linux, Windows, and Network Attached Storage (NAS) environments.

By protecting file system and Oracle Database data, Oracle Secure Backup provides a complete tape backup solution for your IT environment.

Oracle Secure Backup is tightly integrated with RMAN to provide the media management layer for RMAN. With optimized integration points, Oracle Secure Backup and RMAN provide the fastest and most efficient tape backup capability for Oracle Database.

You can back up distributed servers to local and remote tape or disk devices from a central Oracle Secure Backup administrative server using backup policies, calendar-based scheduling for lights out operations, or on-demand backup for immediate requirements. With its highly scalable client/server architecture, Oracle Secure Backup provides local and remote data protection, using Secure Sockets layer (SSL) for secure intradomain communication and two-way server authentication.

Oracle Secure Backup provides the following benefits:

• Optimized performance achieving 25-40% faster Oracle Database backups than comparable media management products with up to 10% less CPU utilization

  • Unused block and undo block compression

  • Shared tape buffers with RMAN

• Policy-based management that allows backup administrators to exercise precise control over the backup domain

• Dynamic drive sharing for increased tape resource use

• Heterogeneous Storage Area Network (SAN) support, enabling NAS, UNIX, Windows, and Linux to share tape drives and media

• File system backup at the file, directory, file system, or raw partition level with full, incremental, and offsite backup scheduling

• Integration with Oracle Enterprise Manager, providing an intuitive, familiar interface

• Backup encryption to tape with policy-based encryption key management leveraging either Oracle Secure Backup host-based encryption or hardware encryption (tape drive)

• Broad tape-device support for new and legacy tape devices in SAN and SCSI environments

• Disk-pool devices to use disk volumes as a backup target

• Network Data Management Protocol (NDMP) support for highly efficient backup of NAS files

• Scalable, low-cost licensing model that reduces IT costs and operational considerations

• Enhanced data throughput Reliable Datagram Socket over Remote Direct Memory Access (RDS/RDMA) over InfiniBand networks for maximum backup and restore performance in Exadata Database Machine environments

• Oracle-aware backup and restoration on Non-Uniform Memory Access (NUMA) machines, ensuring OSB and Oracle Database background processes communicate in the same NUMA region for optimal performance

Oracle RAC and Oracle Clusterware enable Oracle Database to run any packaged or custom application across a set of clustered servers. This capability provides the highest levels of availability and the most flexible scalability. If a clustered server fails, then Oracle Database continues running on the surviving servers. When more processing power is needed, you can add another server without interrupting access to data.

Oracle RAC enables multiple instances that are linked by an interconnect to share access to an Oracle database. In an Oracle RAC environment, Oracle Database runs on two or more systems in a cluster while concurrently accessing a single shared database. The result is a single database system that spans multiple hardware systems, enabling Oracle RAC to provide high availability and redundancy during failures in the cluster. Oracle RAC accommodates all system types, from read-only data warehouse systems to update-intensive online transaction processing (OLTP) systems.

Oracle Clusterware is software that, when installed on servers running the same operating system, enables the servers to be bound together to operate as if they are one server, and manages the availability of user applications and Oracle databases. Oracle Clusterware also provides all of the features required for cluster management, including node membership, group services, global resource management, and high availability functions:

• For high availability, you can place Oracle databases (single-instance or Oracle RAC databases), and user applications (Oracle and non-Oracle) under the management and protection of Oracle Clusterware so that the databases and applications restart when a process fails or so that a failover to another node occurs after a node failure.

• For cluster management, Oracle Clusterware presents multiple independent servers as if they are a single-system image or one virtual server. This single virtual server is preserved across the cluster for all management operations, enabling administrators to perform installations, configurations, backups, upgrades, and monitoring functions. Then, Oracle Clusterware automatically distributes the execution of these management functions to the appropriate nodes in the cluster.

Oracle Clusterware is a requirement for using Oracle RAC. Oracle Clusterware is the only clusterware that you need for most platforms on which Oracle RAC operates. Although Oracle Database continues to support third-party clusterware products on specified platforms, using Oracle Clusterware provides these main benefits:

• Dispenses with proprietary vendor clusterware

• Uses an integrated software stack from Oracle that provides disk management with local or remote Oracle Automatic Storage Management (Oracle Flex ASM) to data management with Oracle Database and Oracle RAC

• Can be configured in large clusters, called an Oracle Flex Cluster.

In addition, Oracle Database features, such as Oracle services, use the underlying Oracle Clusterware mechanisms to provide their capabilities.

Oracle Clusterware requires two clusterware components: a voting disk to record node membership information and the Oracle Cluster Registry (OCR) to record cluster configuration information. The voting disk and the OCR must reside on shared storage. Oracle Clusterware requires that each node be connected to a private network over a private interconnect.

Topics:

• Benefits of Using Oracle Clusterware
  
• Benefits of Using Oracle Real Application Clusters and Oracle Clusterware
  
• Oracle RAC Advantages Over Traditional Cold Cluster Solutions
  

Oracle Real Application Clusters One Node (Oracle RAC One Node) is a single instance of an Oracle RAC database that runs on one node in a cluster. This feature enables you to consolidate many databases into one cluster with minimal overhead, protecting them from both planned and unplanned downtime. The consolidated databases reap the high availability benefits of failover protection, online rolling patch application, and rolling upgrades for the operating system and Oracle Clusterware.

Oracle RAC One Node enables better availability than cold failover for single-instance databases because of the Oracle technology called online database relocation, which intelligently migrates database instances and connections to other cluster nodes for high availability and load balancing. Online database relocation is performed using the Server Control Utility (SRVCTL).

Oracle RAC One Node provides the following:

• Always available single-instance database services

• Built-in cluster failover for high availability

• Live migration of instances across servers

• Online rolling patches and rolling upgrades for single-instance databases

• Online upgrade from single-instance to multiple-instance Oracle RAC

• Better consolidation for database servers

• Enhanced server virtualization

• Lower cost development and test platform for full Oracle RAC

• Relocation of Oracle RAC primary and standby databases configured with Data Guard. This functionality is available starting with Oracle Database 11g Release 2 (11.2.0.2).

Oracle RAC One Node also facilitates the consolidation of database storage, standardizes your database environment, and, when necessary, enables you to transition to a full, multiple-instance Oracle RAC database without downtime or disruption.

Oracle ASM provides a vertically integrated file system and volume manager directly in the Oracle Database kernel, resulting in:

• Significantly less work to provision database storage

• Higher level of availability

• Elimination of the expense, installation, and maintenance of specialized storage products

• Unique capabilities for database applications

For optimal performance, Oracle ASM spreads files across all available storage. To protect against data loss, Oracle ASM extends the concept of SAME (stripe and mirror everything) and adds more flexibility because it can mirror at the database file level rather than at the entire disk level.

More important, Oracle ASM simplifies the processes of setting up mirroring, adding disks, and removing disks. Instead of managing hundreds or possibly thousands of files (as in a large data warehouse), database administrators using Oracle ASM create and administer a larger-grained object called a disk group. The disk group identifies the set of disks that are managed as a logical unit. Automation of file naming and placement of the underlying database files save administrators time and ensure adherence to standard best practices.

The Oracle ASM native mirroring mechanism (two-way or three-way) protects against storage failures. With Oracle ASM mirroring, you can provide an additional level of data protection with the use of failure groups. A failure group is a set of disks sharing a common resource (disk controller or an entire disk array) whose failure can be tolerated. After it is defined, an Oracle ASM failure group intelligently places redundant copies of the data in separate failure groups. This ensures that the data is available and transparently protected against the failure of any component in the storage subsystem.

By using Oracle ASM, you can:

• Mirror and stripe across drives and storage arrays.

• Automatically remirror from a failed drive to remaining drives.

• Automatically rebalance stored data when disks are added or removed while the database remains online.

• Support Oracle database files and non-database files using Oracle Automatic Storage Management Cluster File System (Oracle ACFS).

• Allow for operational simplicity in managing database storage.

• Manage the Oracle Cluster Registry (OCR) and voting disks.

• Provide preferred read capability on disks that are local to the instance, which gives better performance for an extended cluster.

• Support very large databases.

• Support Oracle ASM rolling upgrades.

• Improve availability and reliability using the Oracle ASM disk scrubbing process to find and repair logical data corruptions using mirror disks.

• Support finer granularity in tuning and security.

• Provide fast repair after a temporary disk failure through Oracle ASM Fast Mirror Resync and automatic repair of block corruptions if a good copy exists in one of the mirrors.

• Provide disaster recovery capability for the file system by enabling replication of Oracle ACFS across the network to a remote site.

• Patch the Oracle ASM instance without impacting the clients that are being serviced using Oracle Flex ASM. A database instance can be directed to access Oracle ASM metadata from another location while the current Oracle ASM instance it is connected to is taken offline for planned maintenance.

• Monitor and manage the speed and status of Oracle ASM Disk Resync and Rebalance operations.

• Bring online multiple disks simultaneously and manage performance better by controlling resync parallelism using the Oracle ASM Resync Power Limit. Recover faster after a cell or disk failure, and the instance doing the resync is failing; this is made possible by using a Disk Resync Checkpoint which enables a resync to resume from where it was interrupted or stopped instead of starting from the beginning.

• Automatically connect database instances to another Oracle ASM instance using Oracle Flex ASM. The local database instance can still access the required metadata and data if an Oracle ASM instance fails due to an unplanned outage.

• Use flex diskgroups to prioritize high availability benefits across multiple databases all using the same diskgroup. Some of the key HA benefits are file extent redundancy, rebalance power limit, and rebalance priority. With flex diskgroups, you can set different values for the above features for different databases, resulting in prioritization across multiple databases within one diskgroup.

• Use flex diskgroups to implement quoto_groups across multiple databases sharing one diskgroup which helps in space management and protection.

• Use flex diskgroups to create point-in-time database clones using the ASM split mirror feature.

• Use preferred reads with stretch clusters to improve performance by affinitizing reads to a site.

The fast recovery area is a unified storage location for all recovery-related files and activities in Oracle Database. After this feature is enabled, all RMAN backups, archived redo log files, control file autobackups, flashback logs, and data file copies are automatically written to a specified file system or Oracle ASM disk group, and the management of this disk space is handled by RMAN and the database server.

Performing a backup to disk is faster because using the fast recovery area eliminates the bottleneck of writing to tape. More important, if database media recovery is required, then data file backups are readily available. Restoration and recovery time is reduced because you do not need to find a tape and a free tape device to restore the needed data files and archived redo log files.

The fast recovery area provides the following benefits:

• Unified storage location of related recovery files

• Management of the disk space allocated for recovery files, which simplifies database administration tasks

• Fast, reliable, disk-based backup and restoration

Data block corruptions can be very disruptive and challenging to repair. Corruptions can cause serious application and database downtime and data loss when encountered and worse yet it can go undetected for hours, days and even weeks leading to even longer application downtime once detected. Unfortunately, there is not one way to comprehensively prevent, detect, and repair data corruptions within the database because the source and cause of corruptions can be anywhere in memory, hardware, firmware, storage, operating system, software, or user error. Worse yet, third-party solutions that do not understand Oracle data block semantics and how Oracle changes data blocks do not prevent and detect data block corruptions well. Third party remote mirroring technologies can propagate data corruptions to the database replica (standby) leading to a double failure, data loss, and much longer downtime. Third party backup and restore solutions cannot detect corrupted backups or bad sectors until a restore or validate operation is issued, resulting in longer restore times and once again potential data loss.

Oracle MAA has a comprehensive plan to prevent, detect, and repair all forms of data block corruptions including physical block corruptions, logical block corruptions, stray writes, and lost writes. These additional safeguards provide the most comprehensive Oracle data block corruption prevention, detection, and repair solution. Details of this plan are described in the My Oracle Support note "Best Practices for Corruption Detection, Prevention, and Automatic Repair - in a Data Guard Configuration."

Table 3-1 outlines block corruption checks for various manual operational checks and runtime and background corruption checks. Database administrators and the operations team can incorporate manual checks such as running RMAN backups, RMAN "check logical" validations or running the ANALYZE VALIDATE STRUCTURE command on important objects. Manual checks are especially important to validate data that are rarely updated or queried.

Runtime checks are far superior in that they catch corruptions almost immediately or during runtime for actively queried and updated data. Runtime checks can prevent corruptions or automatically fix corruptions resulting in better data protection and higher application availability. A new background check has been introduced in Exadata to automatically scan and scrub disks intelligently with no application overhead and to automatically fix physically corrupted blocks.

Data Recovery Advisor automatically diagnoses persistent (on-disk) data failures, presents appropriate repair options, and runs repair operations at your request.

You can use Data Recovery Advisor to troubleshoot primary databases, logical standby databases, physical standby databases, and snapshot standby databases.

Data Recovery Advisor includes the following functionality:

• Failure diagnosis

  The first symptoms of database failure are usually error messages, alarms, trace files and dumps, and failed health checks. Assessing these symptoms can be complicated, error-prone, and time-consuming. Data Recovery Advisor automatically diagnoses data failures and informs you about them.

• Failure impact assessment

  After a failure is diagnosed, you must understand its extent and assess its impact on applications before devising a repair strategy. Data Recovery Advisor automatically assesses the impact of a failure and displays it in an easily understood format.

• Repair generation

  Even if a failure was diagnosed correctly, selecting the correct repair strategy can be error-prone and stressful. Moreover, there is often a high penalty for making poor decisions in terms of increased downtime and loss of data. Data Recovery Advisor automatically determines the best repair for a set of failures and presents it to you.

• Repair feasibility checks

  Before presenting repair options, Data Recovery Advisor validates them with respect to the specific environment and availability of media components required to complete the proposed repair, including restoring files directly from the primary or standby database to complete the proposed repair.

• Repair automation

  If you accept the suggested repair option, Data Recovery Advisor automatically performs the repair, verifies that the repair was successful, and closes the appropriate failures.

• Validation of data consistency and database recoverability

  Data Recovery Advisor can validate the consistency of your data, and backups and redo stream, whenever you choose.

• Early detection of corruption

  Through Health Monitor, you can schedule periodic runs of Data Recovery Advisor diagnostic checks to detect data failures before a database process executing a transaction discovers the corruption and signals an error. Early warnings can limit the damage caused by corruption.

• Integration of data validation and repair

  Data Recovery Advisor is a single tool for data validation and repair.

The best protection against human errors is to prevent their occurrence. The best way to prevent human errors is to restrict user access to only those data and services required to perform business functions. Oracle Database provides a wide range of security tools to control access to application data by authenticating database users and then enabling administrators to grant them only those privileges required to perform their duties.

In addition, the Oracle Database security model provides the ability to restrict data access at a row level using Oracle Virtual Private Database, thereby further isolating database users from data that they do not need to access.

Oracle Database provides the following security benefits:

• Authentication control to validate the identities of entities using networks, databases, and applications. Network sessions between databases, such as redo transport sessions, are also authenticated.

• Authorization control to provide limits to access and actions linked by database user identities and roles.

• Access control to objects, providing protection regardless of the entity seeking to access or alter them.

• Auditing control to monitor and gather data about specific database activities, investigate suspicious activity, deter users (or others) from inappropriate activities, and detect problems with authorization or access control implementation.

• Security policy management using profiles.

• Encryption of data residing in the database and backups, or transferred to and from databases.

• Administration of Data Guard configurations can be delegated to a class of users who would not be granted SYSDBA privileges.

• Protecting your data at rest with Transparent Data Encryption can be achieved easily with online conversion to TDE.

Oracle Flashback technology is a group of Oracle Database features that let you view past states of database, database objects, transactions or rows or to rewind the database, database objects, transactions or rows to a previous state without using point-in-time media recovery.

With flashback features, you can:

• Perform queries to show data as it looked at a previous point in time

• Perform queries that return metadata that shows a detailed history of changes to the database

• Recover tables or rows to a previous point in time

• Automatically track and archive transactional data changes

• Roll back a transaction and its dependent transactions while the database remains online

• Undrop a table

• Recover a database to a point-in-time without a restore operation

Other than the flashback database feature, most Oracle Flashback features use the Automatic Undo Management (AUM) system to obtain metadata and historical data for transactions. They rely on undo data, which are records of the effects of individual transactions. For example, if a user runs an UPDATE statement to change a salary from 1000 to 1100, then Oracle Database stores the value 1000 in the undo data.

Undo data is persistent and survives a database shutdown. By using flashback features, you can use undo data to query past data or recover from logical damage. Besides using it in flashback features, Oracle Database uses undo data to perform these actions:

• Roll back active transactions

• Recover terminated transactions by using database or process recovery

• Provide read consistency for SQL queries

Oracle Flashback can address and rewind data that is compromised due to various human or operator errors that inadvertently or maliciously change data, cause bad installations and upgrades, and result in logical errors in applications. These problems are addressed in the following phases, and use features such as flashback transaction, flashback drop, flashback table, and flashback database.

Phase 1: Detection of logical failure, which is usually done by the application.

Phase 2: Error investigation using features such as flashback query, flashback version query, and flashback transaction query and the DBMS_FLASHBACK package.

Phase 3: Error recovery.

Topics:

• Oracle Flashback Query
  
• Oracle Flashback Version Query
  
• Oracle Flashback Transaction
  
• Oracle Flashback Transaction Query
  
• Oracle Flashback Table
  
• Oracle Flashback Drop
  
• Restore Points
  
• Flashback Pluggable Database
  You can rewind a PDB to a previous SCN. The FLASHBACK PLUGGABLE DATABASE command, which is available through SQL or Recovery Manager, is analogous to FLASHBACK DATABASE in a non-CDB.
• Block Media Recovery Using Flashback Logs or Physical Standby Database
  
• Flashback Data Archive
  

Oracle Data Pump technology enables very high-speed movement of data and metadata from one database to another. Data Pump is used to perform the following planned maintenance activities:

• Database migration to a different platform

• Database migration to pluggable databases

• Database upgrade

See Oracle High Availability Solutions for System and Software Maintenance for more information about using this technology for planned maintenance.

The Data Pump features that enable the planned maintenance activities listed above are the following:

• Full transportable export/import to move an entire database to a different database instance

• Transportable tablespaces to move a set of tablespaces between databases

Table 3-2 describes the Oracle replication technologies for non-database files.

Topics:

• Oracle Database File System
  
• Oracle ASM Cluster File System
  
• Oracle Solaris ZFS Storage Appliance Replication
  

A highly available architecture requires the application tier to transparently fail over to a surviving instance or database advertising the required service. This ensures that applications are generally available or minimally impacted in the event of node failure, instance failure, data corruption, or database failures. Transparent client failover enables applications to fail over to another available Oracle RAC instance or to another database (such as in the case of a Data Guard role transition or Oracle GoldenGate).

Client failover encompasses failure notification, connection cleanup, automatic retries and reconnection to a database service residing in another Oracle RAC instance or database and possibly retry the database request.

At a high level, the following components are used to provide for seamless client failover:

• Services

  Oracle Database provides a powerful automatic workload management facility, called services, to enable the enterprise grid vision. Services are entities that you can define in Oracle databases that enable you to group database workloads, route work to the optimal instances that are assigned to offer the service, and achieve high availability for planned and unplanned actions.

• High Availability Framework

  An Oracle RAC component that enables Oracle Database to maintain components in a running state.

• Fast Application Notification (FAN)

  FAN is a high availability notification mechanism that Oracle RAC uses to notify other processes about configuration-level and service-level information that includes service status changes, such as UP or DOWN events. FAN also provides load advisory notifications. The Oracle client drivers and Oracle connection pools respond to FAN events and take immediate action. FAN UP and DOWN events can apply to instances, services, and nodes.

• Transaction Guard

  Transaction Guard is a tool that provides a protocol and an API for at-most-once execution of transactions in case of unplanned outages and duplicate submissions.

• Application Continuity

  Application Continuity provides a general purpose infrastructure that replays the in-flight request when a recoverable error is received, masking many system, communication, and storage outages and hardware failures. Unlike other recovery technologies, this feature attempts to recover the transactional and non-transactional session states beneath the application, so that the outage appears to the application as a delayed execution.

• Connection Load Balancing

  Connection Load Balancing is a feature of Oracle Net Services that balances incoming connections across all of the instances that provide the requested database service.

  With run-time connection load balancing, applications can use load balancing advisory events to provide better service to users. Oracle JDBC, Oracle Universal Connection Pool for Java, OCI session pool, ODP.NET, and Oracle WebLogic Server Active GridLink for Oracle RAC clients are automatically integrated to take advantage of load balancing advisory events. The load balancing advisory informs the client about the current service level that an instance is providing for a service

• Fast Connection Failover

  Fast Connection Failover is the ability of Oracle Clients to provide rapid failover of connections by subscribing to FAN events.

• Transparent Application Failover (TAF)

  Transparent Application Failover is a run-time failover for high availability environments that refers to the failover and re-establishment of application-to-service connections. It enables client applications to automatically reconnect to the database if the connection fails, and, optionally, resume a SELECT statement that was in progress. This reconnection happens automatically from within the Oracle Call Interface (OCI) library.

• Single Client Access Name (SCAN)

  SCAN provides a single name to the clients connecting to Oracle RAC that does not change throughout the life of the cluster, even if you add or remove nodes from the cluster. Clients connecting with SCAN can use a simple connection string, such as a thin JDBC URL or EZConnect, and still achieve the load balancing and client connection failover.

• Global Data Services

  Global Data Services (GDS) is a new capability of Oracle Database that extends the concept of services to a globally replicated configuration involving a combination of single-instance, Oracle RAC, Oracle Active Data Guard, and Oracle GoldenGate. This enables services to be deployed anywhere within this globally replicated configuration, supporting load balancing, high availability, database affinity, and so on.

• Connection Time Failover

  Oracle Net supports connect descriptors with multiple lists of addresses, each with its own characteristics. Connection time failover allows for a new connection attempt to fail over to a different address if the connection to the first address fails.

Topics:

• Client Failover Processing for Connections
  
• Transaction Failover and Protection
  
• Oracle Database with Global Data Services
  

Oracle Multitenant is the optimal database consolidation method from Oracle Database 12c onward. The multitenant architecture combines the best attributes of each of the previous consolidation methods without their accompanying tradeoffs.

Oracle Multitenant helps reduce IT costs by simplifying consolidation, provisioning, upgrades and more. This new architecture allows a container database (CDB) to hold many pluggable databases (PDBs). To applications, these PDBs appear as a standalone database, and no changes are required to the application in order to access the PDB. By consolidating multiple databases as PDBs into a single CDB, you are provided with the ability to manage "many as one". The flexibility remains to operate on PDBs in isolation should your business require it.

Oracle Multitenant is fully compliant with and takes direct advantage of high availability features such as Oracle Real Application Clusters, Oracle Data Guard, and Oracle GoldenGate, just like any non-container database (non-CDB), meaning it can be used in any of the Oracle MAA reference architectures. Grouping multiple PDBs with the same high availability requirements into the same CDB ensures that all of those PDBs and their applications are managed and protected with the same technologies and configurations.

Oracle Sharding is a scalability and availability feature for custom-designed OLTP applications explicitly designed to run on a sharded database.

Oracle sharding enables distribution and replication of data across a pool of Oracle databases that share no hardware or software. The pool of databases is presented to the application as a single logical database. Applications elastically scale (data, transactions, and users) to any level, on any platform, simply by adding additional databases (shards) to the pool. Scaling up to 1000 shards is supported in the first release with Oracle Database 12c Release 2.

Oracle Sharding provides superior run-time performance and simpler life-cycle management compared to home-grown deployments that use a similar approach to scalability. It also provides the advantages of an enterprise DBMS, including  relational schema, SQL, and other programmatic interfaces, support for complex data types, online schema changes, multi-core scalability, advanced security, compression, high-availability, ACID properties, consistent reads, developer agility with JSON, and much more.

Oracle Restart is a new feature in Oracle 11g Release 2 (11.2) that enhances the availability of a single-instance (nonclustered) Oracle database and its components. Oracle Restart is used in single-instance environments only. For Oracle Real Application Clusters (Oracle RAC) environments, the functionality to automatically restart components is provided by Oracle Clusterware.

If you install Oracle Restart, it automatically restarts the database, the listener, and other Oracle components after a hardware or software failure or whenever the database's host computer restarts. It also ensures that the Oracle components are restarted in the proper order, in accordance with component dependencies.

Oracle Restart periodically monitors the health of components—such as SQL*Plus, the Listener Control utility (LSNRCTL), ASMCMD, and Oracle Data Guard—that are integrated with Oracle Restart. If the health check fails for a component, Oracle Restart shuts down and restarts the component.

Oracle Restart runs out of the Oracle Grid Infrastructure home, which you install separately from Oracle Database homes.

Integrated client failover applications depend on role based services and Fast Application Notification events, managed by Oracle clusterware, to alert the application to failures. Single instance databases must have Oracle Restart to achieve integrated client failover.

Oracle Site Guard is a disaster-recovery solution that enables administrators to automate complete site switchover or failover.

Oracle Site Guard orchestrates and automates the coordinated failover of Oracle Fusion Middleware, Oracle Fusion Applications, and Oracle Databases. It is also extensible to include other data center software components.

Oracle Site Guard integrates with underlying replication mechanisms that synchronize primary and standby environments and protect mission critical data. It comes with a built-in support for Oracle Data Guard for Oracle database, and Oracle Sun ZFS. Oracle Site Guard can also support other storage replication technologies.

The cloud-scale Zero Data Loss Recovery Appliance, commonly known as Recovery Appliance, is an engineered system designed to dramatically reduce data loss and backup overhead for all Oracle databases in the enterprise. Integrated with Recovery Manager (RMAN), the Recovery Appliance enables a centralized, incremental-forever backup strategy for large numbers of databases, using cloud-scale, fault-tolerant hardware and storage. The Recovery Appliance continuously validates backups for recoverability.

Recovery Appliance provides is the MAA preferred backup and recovery appliance because:

• Elimination of data loss when restoring from Recovery Appliance

• Minimal backup overhead

• Improved end-to-end data protection visibility

• Cloud-scale protection

• Integrates very well with all MAA reference architectures including Oracle Sharding tier