Senin, 10 Oktober 2011

Oracle Database

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Oracle Database
Oracle logo.svg
Developer(s) Oracle Corporation
Development status Active
Written in C, C++[1]
Available in Multi-lingual
Type ORDBMS
License Proprietary
Website www.oracle.com
The Oracle Database (commonly referred to as Oracle RDBMS or simply as Oracle) is an object-relational database management system (ORDBMS)[2] produced and marketed by Oracle Corporation.
Larry Ellison and his friends and former co-workers Bob Miner and Ed Oates started the consultancy Software Development Laboratories (SDL) in 1977. SDL developed the original version of the Oracle software. The name Oracle comes from the code-name of a CIA-funded project Ellison had worked on while previously employed by Ampex.[3]

Contents

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[edit] Physical and logical structures

An Oracle database system—identified by an alphanumeric system identifier or SID[4]—comprises at least one instance of the application, along with data storage. An instance—identified persistently by an instantiation number (or activation id: SYS.V_$DATABASE.ACTIVATION#)—comprises a set of operating-system processes and memory-structures that interact with the storage. Typical processes include PMON (the process monitor) and SMON (the system monitor).
Users of the Oracle databases refer to the server-side memory-structure as the SGA (System Global Area). The SGA typically holds cache information such as data-buffers, SQL commands, and user information. In addition to storage, the database consists of online redo logs (or logs), which hold transactional history. Processes can in turn archive the online redo logs into archive logs (offline redo logs), which provide the basis (if necessary) for data recovery and for some forms of data replication.
If the Oracle database administrator has implemented Oracle RAC (Real Application Clusters), then multiple instances, usually on different servers, attach to a central storage array. This scenario offers advantages such as better performance, scalability and redundancy. However, support becomes more complex, and many sites do not use RAC. In version 10g, grid computing introduced shared resources where an instance can use (for example) CPU resources from another node (computer) in the grid.
The Oracle DBMS can store and execute stored procedures and functions within itself. PL/SQL (Oracle Corporation's proprietary procedural extension to SQL), or the object-oriented language Java can invoke such code objects and/or provide the programming structures for writing them.

[edit] Storage

The Oracle RDBMS stores data logically in the form of tablespaces and physically in the form of data files ("datafiles").[5] Tablespaces can contain various types of memory segments, such as Data Segments, Index Segments, etc. Segments in turn comprise one or more extents. Extents comprise groups of contiguous data blocks. Data blocks form the basic units of data storage.
There is also a partitioning feature available on newer versions of the database, which allows tables to be partitioned based on different set of keys. Specific partitions can then be easily added or dropped to help manage large data sets.
Oracle database management tracks its computer data storage with the help of information stored in the SYSTEM tablespace. The SYSTEM tablespace contains the data dictionary—and often (by default) indexes and clusters. A data dictionary consists of a special collection of tables that contains information about all user-objects in the database. Since version 8i, the Oracle RDBMS also supports "locally managed" tablespaces which can store space management information in bitmaps in their own headers rather than in the SYSTEM tablespace (as happens with the default "dictionary-managed" tablespaces). Version 10g and later introduced the SYSAUX tablespace which contains some of the tables formerly in the SYSTEM tablespace.

[edit] Disk files

Wiki letter w cropped.svg This section requires expansion.
Disk files primarily consist of the following types:
  • Data and index files: Those files are necessary for the physical storage, which can consist of the data dictionary data (associated to the tablespace SYSTEM), user data, or index data. These files can be managed manually or managed by Oracle itself ("Oracle-managed files"). Note that a datafile has to belong to exactly one tablespace, whereas a tablespace can consist of multiple datafiles.
  • Redo log files consisting of all changes to the database, used to recover from an instance failure. Note that often these files are stored multiple times, for extra security in case of disk failure. The identical redo log files are said to belong to the same group.
  • Undo files: Those special datafiles, which can only contain undo information, are used for recovery, rollbacks, and read consistency.
  • Archive log files: Those files are copies of the redo log files, but are usually stored at different locations. They are necessary for example to be applied to a standby database, or to perform recovery after an instance failure. It is possible to archive to multiple locations.
  • Tempfiles: Those special datafiles are used exclusively for temporary storage data (used for example for large sorts)
  • Control files, necessary for database startup. Note that this file is usually also multiplexed, and is binary. It contains important information such as database name, datafiles names/locations, tablespace names, current log sequence and checkpoint information, ... [6]
At the physical level, data files comprise one or more data blocks, where the block size can vary between data files.
Data files can occupy pre-allocated space in the file system of a computer server, utilize raw disk directly, or exist within ASM logical volumes.[7]
[edit] Control files
The following parameters govern the size of the control files:
* maxlogfile
* maxlogmembers
* maxloghistory
* maxinstances
* control_file_record_keep_time

[edit] Database Schema

Oracle database conventions refer to defined groups of object ownership (generally associated with a "username") as schemas.
Most Oracle database installations traditionally came with a default schema called SCOTT. After the installation process has set up the sample tables, the user can log into the database with the username scott and the password tiger. The name of the SCOTT schema originated with Bruce Scott, one of the first employees at Oracle (then Software Development Laboratories), who had a cat named Tiger.[8]
Oracle Corporation has de-emphasized the use of the SCOTT schema, as it uses few of the features of the more recent releases of Oracle. Most recent examples supplied by Oracle Corporation reference the default HR or OE schemas.
Other default schemas[9][10] include:
  • SYS (essential core database structures and utilities)
  • SYSTEM (additional core database structures and utilities, and privileged account)
  • OUTLN (utilized to store metadata for stored outlines for stable query-optimizer execution plans.[11]
  • BI, IX, HR, OE, PM, and SH (expanded sample schemas[12] containing more data and structures than the older SCOTT schema).

[edit] System Global Area

Main article: System Global Area
Each Oracle instance uses a System Global Area or SGA—a shared-memory area—to store its data and control-information.[13]
Each Oracle instance allocates itself an SGA when it starts and de-allocates it at shut-down time. The information in the SGA consists of the following elements, each of which has a fixed size, established at instance startup:
  • the redo log buffer: this stores redo entries—a log of changes made to the database. The instance writes redo log buffers to the redo log as quickly and efficiently as possible. The redo log aids in instance recovery in the event of a system failure.
  • the shared pool: this area of the SGA stores shared-memory structures such as shared SQL areas in the library cache and internal information in the data dictionary. An insufficient amount of memory allocated to the shared pool can cause performance degradation.

[edit] Library cache

The library cache[14] stores shared SQL, caching the parse tree and the execution plan for every unique SQL statement. If multiple applications issue the same SQL statement, each application can access the shared SQL area. This reduces the amount of memory needed and reduces the processing-time used for parsing and execution planning.

[edit] Data dictionary cache

The data dictionary comprises a set of tables and views that map the structure of the database.
Oracle databases store information here about the logical and physical structure of the database. The data dictionary contains information such as:
  • user information, such as user privileges
  • integrity constraints defined for tables in the database
  • names and datatypes of all columns in database tables
  • information on space allocated and used for schema objects
The Oracle instance frequently accesses the data dictionary in order to parse SQL statements. The operation of Oracle depends on ready access to the data dictionary: performance bottlenecks in the data dictionary affect all Oracle users. Because of this, database administrators should make sure that the data dictionary cache[15] has sufficient capacity to cache this data. Without enough memory for the data-dictionary cache, users see a severe performance degradation. Allocating sufficient memory to the shared pool where the data dictionary cache resides precludes these particular performance problem.

[edit] Program Global Area

The Program Global Area[16][17] or PGA memory-area of an Oracle instance contains data and control-information for Oracle's server-processes.
The size and content of the PGA depends on the Oracle-server options installed. This area consists of the following components:
  • stack-space: the memory that holds the session's variables, arrays, and so on.
  • session-information: unless using the multithreaded server, the instance stores its session-information in the PGA. (In a multithreaded server, the session-information goes in the SGA.)
  • private SQL-area: an which holds information such as bind-variables and runtime-buffers.
  • sorting area: an area in the PGA which holds information on sorts, hash-joins, etc.

[edit] Dynamic performance views

The dynamic performance views (also known as "fixed views") within an Oracle database present information from virtual tables (X$ tables[18]) built on the basis of database memory.[19] Database users can access the V$ views (named after the prefix of their synonyms) to obtain information on database structures and performance.

[edit] Process architectures

[edit] Oracle processes

The Oracle RDBMS typically relies on a group of processes running simultaneously in the background and interacting to monitor and expedite database operations. Typical operating environments might include some of the following individual processes (shown along with their abbreviated nomenclature):[20]
  • advanced queueing processes (Qnnn)[21]
  • archiver processes (ARCn)
  • checkpoint process (CKPT) *REQUIRED*
  • coordinator-of-job-queues process (CJQn): dynamically spawns slave processes for job-queues
  • database writer processes (DBWn) *REQUIRED*
  • dispatcher processes (Dnnn): multiplex server-processes on behalf of users
  • job-queue slave processes (Jnnn)[22]
  • log-writer process (LGWR) *REQUIRED*
  • log-write network-server (LNSn): transmits redo logs in Data Guard environments
  • logical standby coordinator process (LSP0): controls Data Guard log-application
  • media-recovery process (MRP): detached recovery-server process
  • memory-manager process (MMAN): used for internal database tasks such as Automatic Shared Memory Management
  • memory-monitor process (MMON): process for automatic problem-detection, self-tuning and statistics-gathering[23]
  • memory-monitor light process (MMNL): gathers and stores Automatic Workload Repository (AWR) data
  • mmon slaves (Mnnnn—M0000, M0001, etc.): background slaves of the MMON process[24]
  • process-monitor process (PMON) *REQUIRED*
  • process-spawner (PSP0): spawns Oracle processes
  • queue-monitor coordinator process (QMNC): dynamically spwans queue monitor slaves[25]
  • queue-monitor processes (QMNn)
  • recoverer process (RECO)
  • remote file-server process (RFS)
  • shared server processes (Snnn): serve client-requests
  • system monitor process (SMON) *REQUIRED*

[edit] User processes, connections and sessions

Oracle Database terminology distinguishes different computer-science terms in describing how end-users interact with the database:
  • user processes involve the invocation of application software[26]
  • a connection refers to the pathway linking a user process to an Oracle instance[27]
  • sessions consist of specific connections to an Oracle instance.[28] Each session within an instance has a session identifier or "SID"[29] (distinct from the system-identifier SID).

[edit] Concurrency and locking

Oracle databases control simultaneous access to data resources with locks (alternatively documented as "enqueues"[30] ). The databases also utilize "latches" -- low-level serialization mechanisms to protect shared data structures in the System Global Area.[31]

[edit] Configuration

Database administrators control many of the tunable variations in an Oracle instance by means of values in a parameter file.[32] This file in its ASCII default form ("pfile") normally has a name of the format init<SID-name>.ora. The default binary equivalent server paramater file ("spfile") (dynamically reconfigurable to some extent)[33] defaults to the format spfile<SID-name>.ora. Within an SQL-based environment, the views V$PARAMETER[34] and V$SPPARAMETER[35] give access to reading parameter values.

[edit] Internationalization

Oracle Database software comes in 63 language-versions (including regional variations such as British English and American English). Variations between versions cover the names of days and months, abbreviations, time-symbols such as A.M. and A.D., and sorting.[36]
Oracle Corporation has translated Oracle Database error-messages into Arabic, Catalan, Chinese, Czech, Danish, Dutch, English, Finnish, French, German, Greek, Hebrew, Hungarian, Italian, Japanese, Korean, Norwegian, Polish, Portuguese, Romanian, Russian, Slovak, Spanish, Swedish, Thai and Turkish.[37]
Oracle Corporation provides database developers with tools and mechanisms for producing internationalized database applications: referred to internally as "Globalization". [38] ".[39]

[edit] History

[edit] Corporate/technical timeline

  • 1977: Larry Ellison and friends founded Software Development Laboratories.
  • 1979: SDL changed its company-name to "Relational Software, Inc." (RSI) and introduced its product Oracle V2 as an early commercially available relational database system. The version did not support transactions, but implemented the basic SQL functionality of queries and joins. (RSI never released a version 1 - instead calling the first version version 2 as a marketing gimmick.)[40]
  • 1982: RSI in its turn changed its name, becoming known as "Oracle Corporation",[41] to align itself more closely with its flagship product.
  • 1983: The company released Oracle version 3, which it had re-written using the C programming language and which supported COMMIT and ROLLBACK functionality for transactions. Version 3 extended platform support from the existing Digital VAX/VMS systems to include Unix environments.[41]
  • 1984: Oracle Corporation released Oracle version 4, which supported read-consistency.
  • 1985: Oracle Corporation released Oracle version 5, which supported the client–server model—a sign of networks becoming more widely available in the mid-1980s.
  • 1986: Oracle version 5.1 started supporting distributed queries.
  • 1988: Oracle RDBMS version 6 came out with support for PL/SQL embedded within Oracle Forms v3 (version 6 could not store PL/SQL in the database proper), row-level locking and hot backups.[42]
  • 1989: Oracle Corporation entered the application products market and developed its ERP product, (later to become part of the Oracle E-Business Suite), based on the Oracle relational database.
  • 1990: the release of Oracle Applications release 8[41]
  • 1992: Oracle version 7 appeared with support for referential integrity, stored procedures and triggers.
  • 1997: Oracle Corporation released version 8, which supported object-oriented development and multimedia applications.
  • 1999: The release of Oracle8i aimed to provide a database inter-operating better with the Internet (the i in the name stands for "Internet"). The Oracle8i database incorporated a native Java virtual machine (Oracle JVM, also known as "Aurora".[43]).
  • 2000: Oracle E-Business Suite 11i pioneers integrated enterprise application software[41]
  • 2001: Oracle9i went into release with 400 new features, including the ability to read and write XML documents. 9i also provided an option for Oracle RAC, or "Real Application Clusters", a computer-cluster database, as a replacement for the Oracle Parallel Server (OPS) option.
  • 2003: Oracle Corporation released Oracle Database 10g, which supported regular expressions. (The g stands for "grid"; emphasizing a marketing thrust of presenting 10g as "grid computing ready".)
  • 2005: Oracle Database 10.2.0.1—also known as Oracle Database 10g Release 2 (10gR2)—appeared.
  • 2006: Oracle Corporation announces Unbreakable Linux[41]
  • 2007: Oracle Database 10g release 2 sets a new world record TPC-H 3000 GB benchmark result[44]
  • 2007: Oracle Corporation released Oracle Database 11g for Linux and for Microsoft Windows.
  • 2008: Oracle Corporation acquires BEA Systems.
  • 2010: Oracle Corporation acquires Sun Microsystems.

[edit] Version numbering

Oracle products follow a custom release numbering and naming convention. With the Oracle RDBMS 10g release, Oracle Corporation began using the "10g" label in all versions of its major products, although some sources refer to Oracle Applications Release 11i as Oracle 11i.[clarification needed] The suffixes "i" and "g" do not actually represent a low-order part of the version number, as letters typically represent in software industry version numbering; that is, there is no predecessor version of Oracle 10g called Oracle 10f. Instead, the letters stand for "internet" and "grid", respectively.[citation needed] Consequently many simply drop the "g" or "i" suffix when referring to specific versions of an Oracle product.
Major database-related products and some of their versions include:
Since version 5, Oracle's RDBMS release numbering has used the following codes:
  • Oracle v5
  • Oracle v6
  • Oracle7: 7.0.16—7.3.4
  • Oracle8 Database: 8.0.3—8.0.6
  • Oracle8i Database Release 1: 8.1.5.0—8.1.5.1
  • Oracle8i Database Release 2: 8.1.6.0—8.1.6.3
  • Oracle8i Database Release 3: 8.1.7.0—8.1.7.4
  • Oracle9i Database Release 1: 9.0.1.0—9.0.1.5 (patchset as of December 2003)
  • Oracle9i Database Release 2: 9.2.0.1—9.2.0.8 (patchset as of April 2007)
  • Oracle Database 10g Release 1: 10.1.0.2—10.1.0.5 (patchset as of February 2006)
  • Oracle Database 10g Release 2: 10.2.0.1—10.2.0.5 (patchset as of April 2010)
  • Oracle Database 11g Release 1: 11.1.0.6—11.1.0.7 (patchset as of September 2008)
  • Oracle Database 11g Release 2: 11.2.0.1—11.2.0.2 (patchset as of November 2010)
The version-numbering syntax within each release follows the pattern: major.maintenance.application-server.component-specific.platform-specific.
For example, "10.2.0.1 for 64-bit Solaris" means: 10th major version of Oracle, maintenance level 2, Oracle Application Server (OracleAS) 0, level 1 for Solaris 64-bit.
The Oracle Administrator's Guide offers further information on Oracle release numbers.

[edit] Marketing editions

Over and above the different versions of the Oracle database management software developed over time, Oracle Corporation subdivides its product into varying "editions" - apparently for marketing and license-tracking reasons. (Do not confuse the marketing "editions" with the internal virtual versioning "editions" introduced with Oracle 11.2[45]). In approximate order of decreasing scale, we find:
  • Enterprise Edition[46] (EE) includes more features than the 'Standard Edition', especially in the areas of performance and security. Oracle Corporation licenses this product on the basis of users or of processors, typically for servers running 4 or more CPUs. EE has no memory limits, and can utilize clustering using Oracle RAC software.
  • Standard Edition[47] (SE) contains base database functionality. Oracle Corporation licenses this product on the basis of users or of processors, typically for servers running from one to four CPUs. If the number of CPUs exceeds 4 CPUs, the user must convert to an Enterprise license. SE has no memory limits, and can utilize clustering with Oracle RAC at no additional charge.
  • Standard Edition One,[48] (SE1[49] or SEO) introduced with Oracle 10g, has some additional feature-restrictions. Oracle Corporation markets it for use on systems with one or two CPUs. It has no memory limitations.
  • Express Edition[50] ("Oracle Database XE"), introduced in 2005, offers Oracle 10g free to distribute on Windows and Linux platforms. It has a footprint of only 150 MB and is restricted to the use of a single CPU, a maximum of 4 GB of user data. Although it can install on a server with any amount of memory, it uses a maximum of 1 GB.[51] Support for this version comes exclusively through on-line forums and not through Oracle support.
  • Oracle Database Lite,[52] intended for running on mobile devices. The embedded[53] mobile database located on the mobile device can synchronize with a server-based installation.

[edit] Host platforms

Prior to releasing Oracle 9i in 2001, Oracle Corporation ported its database product to a wide variety of platforms. More recently Oracle Corporation has consolidated on a smaller range of operating-system platforms.
As of October 2006, Oracle Corporation supported the following operating systems and hardware platforms for Oracle Database 10g[citation needed]:

[edit] Related software

[edit] Oracle products

  • Oracle Database Firewall[54] analyzes database traffic on a network to prevent threats such as SQL injection.[55]

[edit] Database options

Oracle Corporation refers to some extensions to the core functionality of the Oracle database as "database options".[56] As of 2008 such options include:
This list is incomplete; you can help by expanding it.
In most cases, using these options entails extra licensing costs.[62]

[edit] Suites

In addition to its RDBMS, Oracle Corporation has released several related suites of tools and applications relating to implementations of Oracle databases. For example:

[edit] Database "features"

Apart from the clearly defined database options, Oracle databases may include many semi-autonomous software sub-systems, which Oracle Corporation sometimes refers to as "features" in a sense subtly different from the normal usage of the word. For example, Oracle Data Guard counts officially as a "feature", but the command-stack within SQL*Plus, though a usability feature, does not appear in the list of "features" in Oracle's list.[original research?] Such "features" may include (for example):
  • Active Session History (ASH), the collection of data for immediate monitoring of very recent database activity.[66]
  • Automatic Workload Repository (AWR), providing monitoring services to Oracle database installations from Oracle version 10. Prior to the release of Oracle version 10, the Statspack facility[67] provided similar functionality.
  • Clusterware
  • Data Aggregation and Consolidation
  • Data Guard for high availability
  • Generic Connectivity for connecting to non-Oracle systems.
  • Data Pump utilities, which aid in importing and exporting data and metadata between databases[68]
  • Database Resource Manager (DRM), which controls the use of computing resources.[69]
  • Fine-grained auditing (FGA) (in Oracle Enterprise Edition[70]) supplements standard security-auditing features[71]
  • Flashback for selective data recovery and reconstruction[72]
  • iSQL*Plus, a web-browser-based graphical user interface (GUI) for Oracle database data-manipulation (compare SQL*Plus)
  • Oracle Data Access Components (ODAC), tools which consist of:[73]
    • Oracle Data Provider for .NET (ODP.NET)[74]
    • Oracle Developer Tools (ODT) for Visual Studio
    • Oracle Providers for ASP.NET
    • Oracle Database Extensions for .NET
    • Oracle Provider for OLE DB
    • Oracle Objects for OLE
    • Oracle Services for Microsoft Transaction Server
  • Oracle-managed files (OMF) -- a feature allowing automated naming, creation and deletion of datafiles at the operating-system level.
  • Recovery Manager (rman) for database backup, restoration and recovery
  • SQL*Plus, a program that allows users to interact with Oracle database(s) via SQL and PL/SQL commands on a command-line. Compare iSQL*Plus.
  • Virtual Private Database[75] (VPD), an implementation of fine-grained access control.[76]
This list is incomplete; you can help by expanding it.

[edit] Standalone tools

Users can develop applications in Java and PL/SQL using tools such as Oracle JDeveloper, Oracle Forms, or Oracle Reports. Oracle Corporation has started[clarification needed] a drive toward 'wizard'-driven environments with a view to enabling non-programmers to produce simple data-driven applications.
Oracle SQL Developer, a free graphical tool for database development, allows developers to browse database objects, run SQL statements and SQL scripts, and edit and debug PL/SQL statements. It incorporates standard and customized reporting.

[edit] Other databases marketed by Oracle Corporation

By acquiring other technology in the database field, Oracle Corporation has taken over:
  • TimesTen, a memory-resident database that can cache transactions and synchronize data with a centralized Oracle database server. It functions as a real-time infrastructure software product intended for the management of low-latency, high-volume data, of events and of transactions.
  • BerkeleyDB, a simple, high-performance, embedded database
  • Oracle Rdb, a legacy relational database for the OpenVMS operating system
  • MySQL a relational database purchased as part of its immediate previous owner, Sun Microsystems

[edit] Use

The Oracle RDBMS has had a reputation among novice users as difficult to install on Linux systems.[citation needed] Oracle Corporation has packaged recent versions for several popular Linux distributions in an attempt to minimize installation challenges beyond the level of technical expertise required to install a database server.[citation needed]

[edit] Official support

Users who have Oracle support contracts can use Oracle's "My Oracle Support" web site. The "My Oracle Support" site was known as MetaLink until a re-branding exercise completed in October 2010. The support site provides users of Oracle Corporation products with a repository of reported problems, diagnostic scripts and solutions. It also integrates with the provision of support tools, patches and upgrades.
The Remote Diagnostic Agent or RDA[77] can operate as a command-line diagnostic tool executing a script. The data captured provides an overview of the Oracle Database environment intended for diagnostic and trouble-shooting. Within RDA, the HCVE (Health Check Validation Engine)[78] can verify and isolate host system environmental issues that may affect the performance of Oracle software.

[edit] Database-related guidelines

Oracle Corporation also endorses certain practices and conventions as enhancing the use of its database products. These include:

[edit] Oracle Certification Program

Main article: Oracle Certification Program
The Oracle Certification Program, a professional certification program, includes the administration of Oracle Databases as one of its main certification paths. It contains three levels:
  1. Oracle Certified Associate (OCA)
  2. Oracle Certified Professional (OCP)
  3. Oracle Certified Master (OCM)

[edit] User groups

A variety of official (Oracle-sponsored) and unofficial Oracle User Groups has grown up of users and developers of Oracle databases. They include:

[edit] Market position

[edit] Competition

In the market for relational databases, Oracle Database competes against commercial products such as IBM's DB2 UDB and Microsoft SQL Server. Oracle and IBM tend to battle for the mid-range database market on UNIX and Linux platforms, while Microsoft dominates the mid-range database market on Microsoft Windows platforms. However, since they share many of the same customers, Oracle and IBM tend to support each other's products in many middleware and application categories (for example: WebSphere, PeopleSoft, and Siebel Systems CRM), and IBM's hardware divisions work closely[citation needed] with Oracle on performance-optimizing server-technologies (for example, Linux on zSeries). The two companies have a relationship perhaps[original research?] best described as "coopetition". Niche commercial competitors include Teradata (in data warehousing and business intelligence), Software AG's ADABAS, Sybase, and IBM's Informix, among many others.
In 2007, competition with SAP AG occasioned litigation from Oracle Corporation.[79]
Increasingly, the Oracle database products compete against such open-source software relational database systems as PostgreSQL, Firebird, and MySQL. Oracle acquired Innobase, supplier of the InnoDB codebase to MySQL, in part to compete better against open source alternatives, and acquired Sun Microsystems, owner of MySQL, in 2010. Database products licensed as open source are, by the legal terms of the Open Source Definition, free to distribute and free of royalty or other licensing fees.

[edit] Pricing

Oracle Corporation offers term licensing for all Oracle products. It bases the list price for a term-license on a specific percentage of the perpetual license price. Prospective purchasers can obtain licenses based either on the number of processors in their target server machines or on the number of potential seats ("named users").[80]
Enterprise Edition
As of July 2010, the database that costs the most per machine-processor among Oracle database editions, at $47,500 per processor. The term "per processor" for Enterprise Edition is defined with respect to physical cores and a processor core multiplier (common processors = 0.5*cores). e.g. An 8-processor, 32-core server using Intel Xeon 56XX CPUs would require 16 processor licenses.[81][82]
Standard Edition
Cheaper: it can run on up to four processors but has fewer features than Enterprise Edition—it lacks proper parallelization,[83] etc.; but remains quite suitable for running medium-sized applications.
Standard ONE
Sells even more cheaply, but remains limited to two CPUs. Standard Edition ONE sells on a per-seat basis with a five-user minimum. Oracle Corporation usually sells the licenses with an extra 22% cost for support and upgrades (access to MetaLink—Oracle Corporation's support site) which customers need to renew annually.
Oracle Express Edition (Oracle XE)
An addition to the Oracle database product family (beta version released in 2005, production version released in February 2006), offers a free version of the Oracle RDBMS, but one limited to 11 GB of user data and to 1 GB of memory used by the database (SGA+PGA).[84] XE will use no more than one CPU and lacks an internal JVM. XE runs only on Windows and on Linux, not on AIX, Solaris, HP-UX and the other operating systems available for other editions.
As computers running Oracle often have eight or more processors, the software price can rise into the hundreds of thousands of dollars. The total cost of ownership often exceeds this, as large Oracle installations usually require experienced and trained database administrators to do the set-up properly. Because of the product's large installed base and available training courses, Oracle specialists in some areas have become a more abundant resource than those for more exotic databases. Oracle frequently provides special training offers for database-administrators.
On Linux, Oracle's certified configurations include Oracle's own Oracle Linux and other commercial Linux distributions (Red Hat Enterprise Linux 3, 4 and 5, SuSE SLES 8, 9 and 10, Asianux) which can cost in a range from a few hundred to a few thousand USD per year (depending on processor architecture and the support package purchased).
The Oracle database system can also install and run on freely available Linux distributions such as the Red Hat-based CentOS,[85] or Debian-based systems.[86]

[edit] See also

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