[1] Development began in 1966 to keep track of the bill of materials for the Saturn V rocket of the Apollo program, and the first version on the IBM System/360 Model 65 was completed in 1967 as ICS/DL/I and officially installed in August 1968.

[2] IMS ultimately traces its history to a 1963 contract from NASA to help control the continual list of changes being made to the Apollo command and service module at the North American Rockwell (NAR) plants in Downey, California (Los Angeles area).

[3] Working with Rockwell's Pete Nordyke, they developed a system based on the recently introduced hard disk which could be queried by NAR's network of computer terminals spread through the engineering department.

The team was expanded with twelve people from IBM, ten from NAR, and three from Caterpillar Tractor who also planned to use the system.

In IMS, data is organized into segments (known today as records or structs), each comprising multiple fields, structured hierarchically to manage complex relationships effectively.

[10] For instance, in a customer database, a root segment at the top of the hierarchy may include fields such as phone number, name, and age.

They leverage a Unit of Work (UOW) concept for simplified online reorganization utilities starting from IMS Version 11.

[13] - Introduced in IMS V7, HALDBs extend the capabilities of full function databases to enhance availability and handle large data volumes effectively.

[14] - IMS V9 introduced online reorganization for HALDBs, supporting continuous availability and accommodating data volumes exceeding 40 terabytes.

IMS then invokes its scheduler on the queued transaction to start the business application program in a message processing region.

IMS generally performs faster than Db2 for common tasks, but may require more programming effort to design and maintain for non-primary duties.