An access path is a view of the data in a physical file, in a given key sequence. In terms of performance, some of the overhead of access paths has to do with the amount of work that the operating system (i OS) does to maintain those views. Each time a record is added, deleted, or changed in the physical file, or when the data in the key of a record changes, the operating system may have to update each CA 2E access path belonging to the PHY file. Consequently, the more access paths you build, the more work the operating system may have to do for each record change.
For example, with non-volatile data files (master or table files of relatively unchanging data), the number of access paths built over them is not as important as it is for the number of logical files built over volatile files (transaction files of constantly changing data) because their access paths must be constantly updated. This implies that master files should not contain a mix of master and volatile data. For example, balance-related information (volatile) should not be held in an Item Master file (non-volatile).
For more information on the data modeling and normalization process, see the "Developing a Conceptual Model" chapter in Defining a Data Model.
You can show the difference between the non-volatile and volatile data files using REF and CPT file types respectively. The only difference between the REF and CPT file types is the automatic creation of an edit file and select record function for REF files.
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