What HISAM Provides
The HISAM access method provides indexed access to root segments and sequential access to child segments. The index contains the root segment sequence field values and is maintained in ascending order as part of the physical database.
As with the HSAM method, the hierarchical relationships are reflected in the physical contiguity of the database records.
HISAM uses two data sets: the primary data set and the overflow data set. Both data sets are defined with fixed-length physical records.
Primary Data Set
The primary data set contains the root segment occurrences and as many of their dependent segment occurrences as will fit. The primary data set supports indexing via the root segment sequence field values.
Overflow Data Set
The overflow data set contains the dependent occurrences that will not fit in the primary data set. Chains between the primary and overflow data sets maintain relationships and sequencing.
HISAM supports hierarchical relationships and unidirectional and bidirectional logical relationships with physical pairing. HISAM does not support bidirectional virtual relationships.
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