database In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases sp ...

computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, e ...

, Oracle Real Application Clusters (RAC) — an option for the Oracle Database software produced by

Oracle Corporation Oracle Corporation is an American multinational computer technology corporation headquartered in Austin, Texas. In 2020, Oracle was the third-largest software company in the world by revenue and market capitalization. The company sells da ...

and introduced in 2001 with Oracle9i — provides

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

for clustering and

high availability High availability (HA) is a characteristic of a system which aims to ensure an agreed level of operational performance, usually uptime, for a higher than normal period. Modernization has resulted in an increased reliance on these systems. Fo ...

in Oracle database environments. Oracle Corporation includes RAC with the Enterprise Edition, provided the nodes are clustered using

Oracle Clusterware Oracle Clusterware is the cross-platform cluster software required to run the Real Application Clusters (RAC) option for Oracle Database. It provides the basic clustering services at the operating-system level that enable Oracle Database sof ...

Functionality

Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single

, thus providing clustering. In a non-RAC Oracle database, a single instance accesses a single database. The ''database'' consists of a collection of

data file A data file is a computer file which stores data to be used by a computer application or system, including input and output data. A data file usually does not contain instructions or code to be executed (that is, a computer program). Most of the ...

s, control files, and

redo log Undo is an interaction technique which is implemented in many computer programs. It erases the last change done to the document, reverting it to an older state. In some more advanced programs, such as graphic processing, undo will negate the las ...

s located on

disk Disk or disc may refer to: * Disk (mathematics), a geometric shape * Disk storage Music * Disc (band), an American experimental music band * ''Disk'' (album), a 1995 EP by Moby Other uses * Disk (functional analysis), a subset of a vector sp ...

. The ''instance'' comprises the collection of Oracle-related memory and background processes that run on a computer system. In an Oracle RAC environment, 2 or more instances concurrently access a single database. This allows an application or user to connect to either computer and have access to a single coordinated set of data. The instances are connected with each other through an "Interconnect" which enables all the instances to be in sync in accessing the data.

Aims

The main aim of Oracle RAC is to implement a clustered database to provide performance,

scalability Scalability is the property of a system to handle a growing amount of work by adding resources to the system. In an economic context, a scalable business model implies that a company can increase sales given increased resources. For example, a ...

and resilience & high availability of data at instance level.

Implementation

Oracle RAC depends on the

infrastructure Infrastructure is the set of facilities and systems that serve a country, city, or other area, and encompasses the services and facilities necessary for its economy, households and firms to function. Infrastructure is composed of public and priv ...

component

to coordinate multiple servers and their sharing of data storage. The FAN (Fast Application Notification) technology detects down-states. RAC administrators can use the srvctl tool to manage RAC configurations,

Cache Fusion

Prior to Oracle 9, network-clustered Oracle databases used a storage device as the data-transfer medium (meaning that one node would write a data block to disk and another node would read that data from the same disk), which had the inherent disadvantage of lackluster performance. Oracle 9i addressed this issue: RAC uses a dedicated network connection for communications internal to the cluster. Since all computers/instances in a RAC access the same database, the overall system must guarantee the coordination of data changes on different computers such that whenever a computer queries data, it receives the current version — even if another computer recently modified that data. Oracle RAC refers to this functionality as ''Cache Fusion''. Cache Fusion involves the ability of Oracle RAC to "fuse" the in-memory data

cache Cache, caching, or caché may refer to: Places United States * Cache, Idaho, an unincorporated community * Cache, Illinois, an unincorporated community * Cache, Oklahoma, a city in Comanche County * Cache, Utah, Cache County, Utah * Cache County ...

d physically separately on each computer into a single, global cache.

Networking

The Oracle Grid Naming Service (GNS) handles name resolution in the cluster registry.

Diagnostics

The Trace File Analyzer (TFA) aids in collecting RAC diagnostic data.

Versions

* Oracle Real Application Clusters 12c Release 1 Enterprise Edition. * Oracle Real Application Clusters One Node (RAC One Node) applies RAC to single-node installations running Oracle Database 11g Release 2 Enterprise Edition.

Evolution

Relative to the single-instance Oracle database, Oracle RAC adds additional complexity. While database automation makes sense for single-instance databases, it becomes even more necessary for clustered databases because of their increased complexity. Oracle Real Application Clusters (RAC), introduced with Oracle 9i in 2001, supersedes the Oracle Parallel Server (OPS) database option. Whereas Oracle9i required an external clusterware (known as vendor clusterware like

TruCluster TruCluster is a closed-source high-availability clustering solution for the Tru64 UNIX operating system. It was originally developed by Digital Equipment Corporation (DEC), but was transferred to Compaq Compaq Computer Corporation (sometimes abb ...

Veritas Cluster Server or

Sun Cluster Oracle Solaris Cluster (sometimes Sun Cluster or SunCluster) is a high-availability cluster software product for Solaris, originally created by Sun Microsystems, which was acquired by Oracle Corporation in 2010. It is used to improve the availab ...

) for most of the Unix flavors (except for Linux and Windows where Oracle provided free clusterware called ''Cluster Ready Services'' or ''CRS''), as of Oracle 10g, Oracle's clusterware product was available for all operating systems. With the release of Oracle Database 10g Release 2 (10.2), Cluster Ready Services was renamed to Oracle Clusterware. When using Oracle 10g or higher, Oracle Clusterware is the only clusterware that you need for most platforms on which Oracle RAC operates (except for Tru cluster, in which case you need vendor clusterware). You can still use clusterware from other vendors, if the clusterware is certified for Oracle RAC. In RAC, the write-transaction must take ownership of the relevant area of the database: typically, this involves a request across the cluster interconnection (local IP network) to transfer the data-block ownership from another node to the one wishing to do the write. This takes a relatively long time (from a few to tens of

millisecond A millisecond (from '' milli-'' and second; symbol: ms) is a unit of time in the International System of Units (SI) equal to one thousandth (0.001 or 10−3 or 1/1000) of a second and to 1000 microseconds. A unit of 10 milliseconds may be called ...

s) compared to single database-node using in-memory operations. For many types of applications, the time spent coordinating block access across systems is low relative to the many operations on the system, and RAC will scale comparably to a single system. Moreover, high read-transactional databases (such as data-warehousing applications) work very well under RAC, as no need for ownership-transfer exists. (Oracle 11g has made many enhancements in this area and performs a lot better than earlier versions for read-only workloads.) The overhead on the

resource mastering Resource refers to all the materials available in our environment which are Technology, technologically accessible, Economics, economically feasible and Culture, culturally Sustainability, sustainable and help us to satisfy our needs and wants. R ...

(or ownership-transfer) is minimal for fewer than three nodes, as the request for any resource in the cluster can be obtained in a maximum of three hops (owner-master-requestor). This makes Oracle RAC horizontally scalable with many nodes. Application vendors (such as

SAP Sap is a fluid transported in xylem cells (vessel elements or tracheids) or phloem sieve tube elements of a plant. These cells transport water and nutrients throughout the plant. Sap is distinct from latex, resin, or cell sap; it is a separ ...

) use Oracle RAC to demonstrate the scalability of their application. Most of the biggest

OLTP In online transaction processing (OLTP), information systems typically facilitate and manage transaction-oriented applications. This is contrasted with online analytical processing. The term "transaction" can have two different meanings, both of w ...

benchmarks are on Oracle RAC. Oracle RAC 11g supports up to 100 nodes. For some applications, RAC may require careful application partitioning to enhance

performance A performance is an act of staging or presenting a play, concert, or other form of entertainment. It is also defined as the action or process of carrying out or accomplishing an action, task, or function. Management science In the work place ...

. An application that scales

linearly Linearity is the property of a mathematical relationship (''function'') that can be graphically represented as a straight line. Linearity is closely related to '' proportionality''. Examples in physics include rectilinear motion, the linear r ...

on an SMP machine may scale linearly under RAC. However, if the application cannot scale linearly on SMP, it will not scale when ported to RAC. In short, the application

is based on how well the application scales in a single instance.

Competitive context

Shared-nothing A shared-nothing architecture (SN) is a distributed computing architecture in which each update request is satisfied by a single node (processor/memory/storage unit) in a computer cluster. The intent is to eliminate contention among nodes. Nodes do ...

and shared-everything architectures each have advantages over the other. DBMS vendors and industry analysts regularly debate the matter; for example,

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...

touts a comparison of its

SQL Server 2005 The history of Microsoft SQL Server begins with the first Microsoft SQL Server database product – SQL Server v1.0, a 16-bit relational database for the OS/2 operating system, released in 1989. Versions Detailed history Genesis On June 12, 198 ...

with Oracle 10g RAC. Oracle Corporation offered a Shared Nothing architecture RDBMS with the advent of the IBM SP and SP2 with the release of 7.x MPP editions, in which virtual shared drives (VSD) were used to create a Shared Everything implementation on a Shared Nothing architecture.

Shared-Everything

''Shared-everything'' architectures share both data on disk and data in memory between nodes in the cluster. This is in contrast to "shared-nothing" architectures that share none of them. Some commercially available databases offer a "shared-everything" architecture.

IBM Db2 Db2 is a family of data management products, including database servers, developed by IBM. It initially supported the relational model, but was extended to support object–relational features and non-relational structures like JSON a ...

for

z/OS z/OS is a 64-bit operating system for IBM z/Architecture mainframes, introduced by IBM in October 2000. It derives from and is the successor to OS/390, which in turn was preceded by a string of MVS versions.Starting with the earliest: * O ...

(the IBM mainframe operating-system) has provided a high-performance data-sharing option since the mid-1990s when IBM released its mainframe hardware and software-clustering infrastructure. In late 2009, IBM announced DB2 pureScale, a shared-disk clustering scheme for DB2 9.8 on AIX that mimics the parallel

sysplex In computing, a Parallel Sysplex is a cluster of IBM mainframes acting together as a single system image with z/OS. Used for disaster recovery, Parallel Sysplex combines data sharing and parallel computing to allow a cluster of up to 32 systems ...

implementation behind Db2 data sharing on the mainframe. In February 2008, Sybase released its Adaptive Server Enterprise, Cluster Edition. It resembles Oracle RAC in its shared-everything design. Although technically not shared-everything, Sybase also provides a column-based relational database focused on analytic and datawarehouse applications called Sybase IQ that can be configured to run in a shared disk mode. Cloud Native Databases, such as

Amazon Aurora Amazon Aurora is a relational database service developed and offered by Amazon Web Services beginning in October 2014. Aurora is available as part of the Amazon Relational Database Service (RDS). History Aurora offered MySQL compatible servic ...

and POLARDB of

Alibaba Cloud Alibaba Cloud, also known as Aliyun (), is a cloud computing company, a subsidiary of Alibaba Group. Alibaba Cloud provides cloud computing services to online businesses and Alibaba's own e-commerce ecosystem. Its international operations are re ...

, are implemented with "shared-everything" architecture on top of cloud-based distributed file system.

Shared-nothing

''Shared-nothing'' architectures share neither the data on disk nor the data in memory between nodes in the cluster. This is in contrast to "shared-everything" architectures, which share both. Competitive products offering shared-nothing architectures include: *

MySQL Cluster MySQL Cluster is a technology providing shared-nothing clustering and auto-sharding for the MySQL database management system. It is designed to provide high availability and high throughput with low latency, while allowing for near linear sca ...

(Oracle Corporation has owned MySQL since 2009) * ScaleBase *

Clustrix Clustrix, Inc. is a San Francisco-based private company founded in 2006 that develops a database management system marketed as NewSQL. History Clustrix was founded in November 2006, and is sometimes called ''Sprout-Clustrix'' as it formed with t ...

*HP NonStop *

IBM InfoSphere IBM InfoSphere DataStage is an ETL tool and part of the IBM Information Platforms Solutions suite and IBM InfoSphere. It uses a graphical notation to construct data integration solutions and is available in various versions such as the Server Ed ...

Warehouse editions that include the Database Partitioning Feature (formerly known as DB2 Extended Enterprise Edition) *

MarkLogic MarkLogic Corporation is an American software business that develops and provides an enterprise NoSQL database, also named ''MarkLogic''. The company was founded in 2001 and is based in San Carlos, California. MarkLogic is a privately held comp ...

Greenplum Greenplum is a big data technology based on MPP architecture and the Postgres open source database technology. The technology was created by a company of the same name headquartered in San Mateo, California around 2005. Greenplum was acquired ...

Oracle NoSQL Database Oracle NoSQL Database is a NoSQL-type distributed key-value database from Oracle Corporation. It provides transactional semantics for data manipulation, horizontal scalability, and simple administration and monitoring. Oracle NoSQL Database Cl ...

Paraccel ParAccel, Inc. was a California-based software company. It provided a database management system designed to provide advanced analytics for business intelligence. ParAccel was acquired by Actian in April 2013. History ParAccel was a venture-b ...

Netezza IBM Netezza (pronounced ne-teez-a) is a subsidiary of American technology company IBM that designs and markets high-performance data warehouse appliances and advanced analytics applications for uses including enterprise data warehousing, busin ...

(aka. Netezza Performance Server) *

Teradata Teradata Corporation is an American software company that provides cloud database and analytics-related software, products, and services. The company was formed in 1979 in Brentwood, California, as a collaboration between researchers at Caltech ...

Vertica Vertica Systems is an analytic database management software company. Vertica was founded in 2005 by the database researcher Michael Stonebraker, with Andrew Palmer as the founding CEO. Ralph Breslauer and Christopher P. Lynch served as later ...

Apache Cassandra Cassandra is a free and open-source, distributed, wide-column store, NoSQL database management system designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure. Cassand ...

, wide column store NoSQL database. *

Apache HBase HBase is an open-source non-relational distributed database modeled after Google's Bigtable and written in Java. It is developed as part of Apache Software Foundation's Apache Hadoop project and runs on top of HDFS (Hadoop Distributed File Sys ...

MongoDB MongoDB is a source-available cross-platform document-oriented database program. Classified as a NoSQL database program, MongoDB uses JSON-like documents with optional schemas. MongoDB is developed by MongoDB Inc. and licensed under the Serve ...

, document-oriented database. *

Couchbase Server Couchbase Server, originally known as Membase, is an open-source, distributed ( shared-nothing architecture) multi-model NoSQL document-oriented database software package optimized for interactive applications. These applications may serve many ...

Riak Riak (pronounced "ree-ack" ) is a distributed NoSQL key-value data store based on Amazon's Dynamo paper, including its "tunable AP" approach, that is tunable consistency, to the tradeoffs imposed by the CAP Theorem. Riak offers high availability, ...

SAP HANA SAP HANA (HochleistungsANalyseAnwendung or High-performance ANalytic Application) is an in-memory, column-oriented, relational database management system developed and marketed by SAP SE. Its primary function as the software running a databa ...

CUBRID CUBRID ( "cube-rid") is an open-source SQL-based relational database management system (RDBMS) with object extensions developed by CUBRID Corp. for OLTP. The name CUBRID is a combination of the two words ''cube'' and ''bridge'', ''cube'' standi ...

References

{{Reflist, 1

External links

Oracle RAC Documentation
(official website from

)
A Step-By-Step Project Guide for Implementing Oracle RACOracle Real Application Clusters and Industry Trends in Cluster Parallelism and Availability
Oracle software Cluster computing