The retrieve APIs allow you to control the performance cost for information you retrieve.
The format specified for any API influences the performance cost of the API. In general, when more information is returned, the performance is slower.
Some list APIs, such as list jobs, list spooled files, and list objects, generate the list with minimal cost. This is why these formats do not retrieve very much information. Some of the APIs, such as list record formats and list fields, have only one format, because there is no additional performance cost to supply the complete information.
The retrieve APIs, such as retrieve member description and retrieve spooled file attributes, have formats that are generally ordered from fastest performance to slowest performance. That is, the lower numbered formats run faster but retrieve less information, and the higher numbered formats run slower but retrieve more information. One exception is the Retrieve Job Information (QUSRJOBI) API where the order of the formats does not have anything to do with performance characteristics. For more information about the performance characteristics for the QUSRJOBI API formats, see the Retrieve Job Information (QUSRJOBI) API in Work Management APIs.