Model 204  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, and first deployed in 1972. It incorporates a programming language and an environment for application development. Implemented in assembly language for IBM System/360 and its successors, M204 can deal with very large databases and transaction loads of 1000 TPS. 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. It has been described as "one of the three major inverted-list [database systems] ... the other two being" ADABAS and ADR's Datacom/DB. 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. Model 204 is commonly used in government and military applications. It is used commercially in the UK by Marks & Spencer. It is also used at the Ventura County Property Tax system in California, the Harris County, Texas, Justice Information Management System, 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. Beginning in 1986, it was used by the US Navy Fleet Intelligence Center Europe and Atlantic (FICEURLANT). Add-on products for Model 204 database were formerly available from Sirius Software, Inc.  Sirius, located in Cambridge, Massachusetts, USA, was acquired by Rocket Software in 2012.