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 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.
An informal list of past and present Model 204 users, compiled in 2010, identified more than 140 organizations worldwide.
Services Australia have used it for their ISIS system that pays over $110 billion in welfare payments to around 6 million Australians.
[19] In a 2014 media interview, then Treasurer of Australia Joe Hockey stated that the Australian social security system and the Pentagon were the only remaining active Model 204 customers in the world.