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How to Count ILFs and EIFs

Internal logical files (ILFs) and external interface files (EIFs) should be counted as logical groupings of data, not physical representations or tables of those groupings of data. An ILF must not be dependent on or attributive to another ILF to maintain its existence. Optional or mandatory subgroups (such as multiple types of payments with different fields for each payment type, but with additional common fields) and attributive groups (such as address tables or contact tables that could belong to one or more higher-level groupings) must be merged with their parents. It is possible but very unlikely that the logical grouping will match the physical implementation. ILFs and EIFs should be counted in a logical manner, regardless of the database structure. An application should be counted with the same number of ILFs and EIFs whether the physical file structure consists of flat files, an IDMS database, an IMS database, a relational database, DB2 tables, or objects.

A particular application contains 10 identical databases to handle 10 different sales regions. The databases are identical in format, but the users want them maintained separately. How many internal logical files (ILFs) should be counted?

One. Although it takes extra effort to maintain 10 different databases, logically the data is the same, regardless of whether it is maintained in separate databases or in a single database.

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