Sidebar: IBM Datasets
A sequential dataset is like a UNIX flat file, that
is, records are read
in order, sequentially one after the other. A partitioned
file contains
several parts and each part has a name. A partitioned
dataset is the
closest thing to the UNIX directory hierarchy that the
mainframe has to
offer; however, unlike UNIX's multiple directory tier
structure, a
partitioned dataset goes down only one level, to its
member. When
processing a partitioned dataset, each part (or member)
is accessed by
its name and then read sequentially.
Indexed sequential datasets consist of an index and
collection of data
records. Records are accessed via a key. Indexed sequential
datasets are
essentially structured database tables. Direct access
datasets are
accessed via the actual disk address in which the record
exists.
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