In CODASYL network databases, immediately superior and subordinate record types (known as a set when combined) are connected to each other with circular chains of next pointers.
In a CODASYL network database, direct access via hashing to any record type of one's choosing is tempting, but the absence of hashing provides faster access when an ordered subset of the occurences of a record type have to be retrieved from an occurrence of the superior or owner record type of the set they are in.
To begin with, every relational table that was directly derived from the root segment of an IMS hierarchy or a hashed CODASYL network record must be indexed or hashed on the equivalent key fields (e.
The same can be done for CODASYL network record types.
Again, this introduces data redundancy, but from a physical design viewpoint, what is discussed as denormalization in relational databases is the same as combining linked segments together in an IMS database or collapsing sets into records in a CODASYL network database.
As a final note here, there are a variety of optional pointers that can be introduced into IMS and CODASYL network database to improve performance.
Note that in a CODASYL network database, any record type can be stored with a hashing routine.
The result is the recognition of the one-to-many relationship between organizations and officers and, from a strictly logical IMS or CODASYL point of view, the repetition of the ONAME field in the Officer segment.
The situation would be similar in the CODASYL network database in Figure 2 if the Room record type is stored via set, relative to the Hotel record type, rather than being stored via cale with a hashing routine.
While many-to-many relationships are handled in CODASYL network database in a fundamentally similar method to IMS, it tends to be somewhat simpler in the design stage but more complicated for the application programmer to use.
In the CODASYL network database in Figure 2, a single juncture record between the Hotel and Conventions records, H-C, serves the same purpose.