HIDAM database structure
A HIDAM database consists of two data sets: a HIDAM primary index and the main database.
The primary HIDAM index is a VSAM KSDS (Pointer Checker does not support ISAM). The main database is a VSAM ESDS or OSAM data set.
The following figure shows how the database record would exist in a HIDAM database.
After initial load, segments within a database record will be grouped together in blocks/CIs in hierarchical order. After update activity, this may not be the case. The following figure represents the status after some update activity: SEGC1, SEGE1, SEGE2, SEGG2, and SEGG4 were inserted.
Once a segment has been inserted in a HIDAM database, the segment is never moved in order to preserve all the direct address pointers. The example assumes physical child first pointers and twin forward pointers are specified for all segment types.
If segments are deleted from the database segment, they will be physically deleted from the data set, and the space will be designated as free space.
If the database used multiple data set groups, each secondary data set group would have the format of the main part of the HIDAM database.
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