DBM (컴퓨팅)

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DBM은 컴퓨팅에서 데이터에 대한 고속의 단일 키 접근을 제공하는 라이브러리이자 파일 포맷이다.[1][2][3]


오리지널 dbm 라이브러리와 파일 포맷은 단순한 데이터베이스 엔진이었으며 켐 톰프슨에 의해 개발되었고 1979년 AT&T에 의해 공개되었다. 이 3 문자는 DataBase Manager에서 비롯된 것이다.


오리지널 AT&T dbm 라이브러리는 여러 구현체로 대체되었다. 그 예로 다음과 같다:[3]


  1. Kew 2007, 80쪽: "DBMs have been with us since the early days of computing, when the need for fast keyed lookups was recognized. The original DBM is a UNIX-based library and file format for fast, highly-scalable keyed access to data. It was followed (in order) by NDBM ('new DBM'), GDBM ('GNU DBM'), and the Berkeley DB. This last is by far the most advanced, and the only DBM under active development today. Nevertheless, all of the DBMs from NDBM onward provide the same core functionality used by most programs, including Apache. A minimal-implementation SDBM is also bundled with APR, and is available to applications along with the other DBMs.
    Although NDBM is now old - like the city named New Town ('Neapolis') by the Greeks in about 600BC and still called Naples today - it remains the baseline DBM. NDBM was used by early Apache modules such as the Apache 1.x versions of mod_auth_dbm and mod_rewrite. Both GDBM and Berkeley DB provide NDBM emulations, and Linux distributions ship with one or other of these emulations in place of the 'real' NDBM, which is excluded for licensing reasons. Unfortunately, the various file formats are totally incompatible, and there are subtle differences in behaviour concerning database locking. These issues led a steady stream of Linux users to report problems with DBMs in Apache 1.x."
  2. Hazel 2001, 500쪽: "The most common [single-key] format is called DBM. Most modern versions of Unix have a DBM library installed as standard, though this is not true of some older systems. The two most common DBM libraries are ndbm (standard on Solaris and IRIX) and Berkeley DB Version 2 or 3 (standard on several free operating systems). Exim supports both of these, as well as the older Berkeley DB Version 1, gdbm, and tdb."
  3. Ladd & O'Donnell 2001, 823-824쪽: "Most UNIX systems have some kind of DBM database. DBM is a set of library routines that manages data files consisting of key and value pairs. The DBM routines control how users enter and retrieve information from the database. Although it isn't the most powerful mechanism for storing information, using DBM is a faster method of retrieving information than using a flat file. Because most UNIX sites use one of the DBM libraries, the tools you need to store your information in a DBM database are readily available.
    Almost as many flavors of the DBM libraries exist as there are UNIX systems. Although most of these libraries are compatible with each other, they all basically work the same way...
    A list follows of some of the most popular DBM libraries available:
    • DBM - DBM stores the database in two files. The first has the extension .Pag and contains the bitmap. The second, which has the extension .Dir, contains the data.
    • NDBM - NDBM is much like DBM but with a few additional features; it was written to provide better storage and retrieval methods. Also, NDBM enables you to open many databases, unlike DBM, in which you are allowed to have only one database open within your script. Like DBM, NDBM stores its information in two files using the extensions .Pag and .Dir.
    • SDBM - SDBM comes with the Perl archive, which has been ported to many platforms. Therefore, you can use DBM databases as long as a version of Perl exists for your computer. SDBM was written to match the functions provided with NDBM, so portability of code shouldn't be a problem. Perl is available on just about all popular platforms.
    • GDBM - GDBM is the GNU version of the DBM family of database routines. GDBM also enables you to cache data, reducing the time that it takes to write to the database. The database has no size limit; its size depends completely on your system's resources. GDBM database files have the extension .Db. Unlike DBM and NDBM, both of which use two files, GDBM only uses one file.
    • Berkeley db - The Berkeley db expands on the original DBM routines significantly. The Berkeley db uses hashed tables the same as the other DBM databases, but the library also can create databases based on a sorted balanced binary tree (BTREE) and store information with a record line number (RECNO). The method that you use depends completely on how you want to store and retrieve the information from a database. Berkeley db creates only one file, which has no extension."
  4. “GDBM”. 《www.gnu.org.ua》. 
  5. yigit, ozan. “sdbm.bun”. 《cse.yorku.ca》. 2019년 5월 8일에 확인함. 
  6. “class SDBM”. 《Documentation for Ruby 2.4.0》. Note that Ruby comes with the source code for SDBM, while the DBM and GDBM standard libraries rely on external libraries and headers. 
  7. “Tokyo Cabinet第1版基本仕様書” [Fundamental Specifications of Tokyo Cabinet Version 1]. 《Fall Labs》 (일본어). 5 August 2010. 28 October 2018에 원본 문서 (html)에서 보존된 문서. 25 May 2019에 확인함. Tokyo CabinetはGDBMやQDBMの後継として次の点を目標として開発されました。これらの目標は達成されており、Tokyo Cabinetは従来のDBMを置き換える製品だと言えます。