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Berkeley DB (BDB) is a software library that provides a high-performance embedded database for key/value data. Berkeley DB is written in C with API bindings for C++, C#, PHP, Java, Perl, Python, Ruby, Tcl, Smalltalk, and many other programming languages. BDB stores arbitrary key/data pairs as byte arrays, and supports multiple data items for a single key. Berkeley DB is not a relational database.〔(Berkeley DB Reference Guide: What is Berkeley DB not? ). Doc.gnu-darwin.org (2001-05-31). Retrieved on 2013-09-18.〕 BDB can support thousands of simultaneous threads of control or concurrent processes manipulating databases as large as 256 terabytes,〔http://doc.gnu-darwin.org/am_misc/dbsizes.html Berkeley DB Reference Guide: Database limits Retrieved on 2013-09-19〕 on a wide variety of operating systems including most Unix-like and Windows systems, and real-time operating systems. "Berkeley DB" is also used as the common brand name for three distinct products: Oracle Berkeley DB, Berkeley DB Java Edition, and Berkeley DB XML. These three products all share a common ancestry and are currently under active development at Oracle Corporation. == Origin == Berkeley DB originated at the University of California, Berkeley as part of BSD, Berkeley's version of the Unix operating system. After 4.3BSD (1986), the BSD developers attempted to remove or replace all code originating in the original AT&T Unix from which BSD was derived. In doing so, they needed to rewrite the Unix database package. A non-AT&T-copyrighted replacement, due to Seltzer and Yigit, attempted to create a disk hash table that performed better than any of the existing Dbm libraries. Berkeley DB itself was first released in 1991 and later included with 4.4BSD. In 1996 Netscape requested that the authors of Berkeley DB improve and extend the library, then at version 1.86, to suit Netscape's requirements for an LDAP server and for use in the Netscape browser. That request led to the creation of Sleepycat Software. This company was acquired by Oracle Corporation in February 2006, which continues to develop and sell Berkeley DB. Since its initial release, Berkeley DB has gone through various versions. Each major release cycle has introduced a single new major feature generally layering on top of the earlier features to add functionality to the product. The 1.x releases focused on managing key/value data storage and are referred to as "Data Store" (DS). The 2.x releases added a locking system enabling concurrent access to data. This is what is known as "Concurrent Data Store" (CDS). The 3.x releases added a logging system for transactions and recovery, called "Transactional Data Store" (TDS). The 4.x releases added the ability to replicate log records and create a distributed highly available single-master multi-replica database. This is called the "High Availability" (HA) feature set. Berkeley DB's evolution has sometimes led to minor API changes or log format changes, but very rarely have database formats changed. Berkeley DB HA supports online upgrades from one version to the next by maintaining the ability to read and apply the prior release's log records. The FreeBSD and OpenBSD operating systems continue to use Berkeley DB 1.8x for compatibility reasons;〔(【引用サイトリンク】title=db(3) )〕 Linux-based operating systems commonly include several versions to accommodate for applications still using older interfaces/files. Starting with the 6.0/12c releases, all Berkeley DB products are licensed under the GNU AGPL.〔([Berkeley DB Announce] Major Release: Berkeley DB 12gR1 (12.1.6.0) ). Retrieved July 5, 2013.〕 Up until then Berkeley DB was redistributed under the 4-clause BSD license (before version 2.0), and the Sleepycat Public License, which is an OSI-approved open-source license as well as an FSF-approved free software license. The product ships with complete source code, build script, test suite, and documentation. The code quality and general utility along with the licensing terms have led to its use in a multitude of free and open-source software. Those who do not wish to abide by the terms of the GNU AGPL, or use an older version with the Sleepycat Public License, have the option of purchasing another proprietary license for redistribution from Oracle Corporation. This technique is called dual licensing. Berkeley DB includes compatibility interfaces for some historic Unix database libraries: dbm, ndbm and hsearch (a System V library for creating in-memory hash tables). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Berkeley DB」の詳細全文を読む スポンサード リンク
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