Model 204

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Model 204 (M204) is a database management system for IBM and compatible mainframe computers developed and commercialized by Computer Corporation of America. It was announced in 1965,[1]: 66 [2] and first deployed in 1972. It incorporates a programming language and an environment for application development. Implemented in assembly language[2] for IBM System/360 and its successors, M204 can deal with very large databases[3] and transaction loads of 1000 TPS.[1]: 4 

Product description[edit]

Model 204 relies on its own type of bitmap index, originally devised by Bill Mann, and combines the use of hash table, B-tree, and partitioned record list technologies to optimize speed and efficiency of database access.[4][5]

It has been described as "one of the three major inverted-list [database systems] ... the other two being" ADABAS and ADR's Datacom/DB.[6]

Although M204 is a pre-SQL (and pre-relational) database product, it is possible to manually map the files of an M204 database to approximate SQL equivalents and provide some limited SQL functionality using Model 204 SQL Server.[7]


Model 204 is commonly used in government and military applications.[8][9][10]

It is used commercially in the UK by Marks & Spencer.[citation needed] It is also used at the Ventura County Property Tax system in California,[11] the Harris County, Texas, Justice Information Management System,[12] and in the New York City Department of Education's Automate The Schools system. An informal list of past and present Model 204 users, compiled in 2010, identified more than 140 organizations worldwide.[13] Beginning in 1986, it was used by the US Navy Fleet Intelligence Center Europe and Atlantic (FICEURLANT).[14]

Model 204 has been a central part of Australian social security for decades. Services Australia have used it for their ISIS system that pays over $110 billion in welfare payments to around 6 million Australians.[15] A 1.5 billion Australian dollar project to replace ISIS was expected to be completed in 2022 but has experienced delays.[16][17][18] The project was scrapped in July 2023 having spent AUD 191 million, with the complexity of encoding social security entitlement rules into Model 204 cited as one of the reasons for its failure.[19]

Corporate information[edit]

Add-on products for Model 204 database were formerly available from Sirius Software, Inc.[20] Sirius, located in Cambridge, Massachusetts, USA, was acquired by Rocket Software in 2012.[21]

See also[edit]


  1. ^ a b Scinta, Gina (2005-10-10). "Model 204 v6r1: Opening New Doors" (PDF). Computer Corporation of America. Archived from the original (PDF) on January 24, 2013. Retrieved 2012-10-26.
  2. ^ a b "Model 204, A Novel DBMS and Application Platform". Sirius Software. Archived from the original on 2012-10-10. Retrieved 2012-10-26.
  3. ^ "with Model 204 you get excellent performance, even with large databases and ... of America's largest companies— for financial applications, inventory control." "Model 204 database". ComputerWorld. December 1980. p. 36.
  4. ^ O'Neil, Patrick (1987). "Model 204 Architecture and Performance". Proceedings of the 2nd International Workshop on High Performance Transaction Systems. Springer-Verlag. pp. 40–59.
  5. ^ Sandy Stanhope, Database Administrator. "What is Model 204?". The Youngstown State University Computing Newsletter. Department of Computer Services. Archived from the original on 18 November 2002. Retrieved 11 January 2008.
  6. ^ "Software AG memories". March 25, 2011. ADABAS was .. one of the three major inverted-list DBMS, the other two being Computer Corporation of America's Model 204 and ADR's DATACOM/DB.
  7. ^ "Rocket Model 204 SQL Server Users Guide". Rocket Software. May 2012. Archived from the original on 2013-02-01. Retrieved 2012-10-27.
  8. ^ "Model 204 is commonly used in government and military applications. Among other things, it runs Australia's social security system." "What is Model 204?". December 17, 2013.
  9. ^ Rodney Gedda (Techworld Australia) (May 2009). "Centrelink ups IT reform, keeps Model 204 'legacy'". Retrieved 9 February 2011.
  10. ^ "County of Ventura Technology Infrastructure Strategic Plan" (PDF). Gartner. 2005-07-13. p. 43. Retrieved 2012-10-25.
  11. ^ "Model 204 Civil Inquiry Manual" (PDF). Harris County, Texas. June 2007. Retrieved 2012-10-25.
  12. ^ Paul Keshvari; et al. (2010). "M204 Client List". Archived from the original on 2013-11-11. Retrieved 2012-10-28.
  13. ^ Fleet Intelligence Center Europe and Atlantic: Command History: 1 January 1986 – 31 December 1986. United States Navy. pp. III-B-3, III-B-7. Retrieved 2016-05-02.
  14. ^ "System Redevelopment — Managing Risks While Planning Transition". 30 June 2018.
  15. ^ "Centrelink's mainframe due for costly update". ZDNet.
  16. ^ "Centrelink to replace crucial mainframe welfare calculator".
  17. ^ "Billion-dollar IT project likely to miss key goal". 28 September 2020.
  18. ^ Crozier, Ry (11 Sep 2023). "Centrelink's canned $191m engine took minutes to do what existing system did in seconds". IT News. Retrieved 12 Sep 2023.
  19. ^ not to be confused with the video-game publisher described at Sirius Software that opened and folded in the 1980s.
  20. ^ Seiffert, Don (2012-11-29). "Rocket Software buys fifth company this year". Boston Business Journal. Retrieved 2016-05-02.

External links[edit]