RDBMS - Auxiliary Data Structure (ADS)


Auxiliary data structures are logical replications of data from one or more columns of a table.

Auxiliary data structures contain copies of, references to, or data computed from base table data, deleting data from an auxiliary data structure does not result in the loss of base table data in that it is still contained in the base table data structure.

In contrast, deleting data from a base table data structure does result in the loss of base table data.

They are therefore derived data.



There are two types of auxiliary data structures:

  • Implicit (ADS)
  • and explicit. (EADS)


An explicit auxiliary data structure (EADS) is created as a consequence of a directive (e.g. DDL, session options, global configuration parameters).

These directives are called EADS Directives.


Any ADS which is not an EADS is by definition an Implict ADS (IADS).

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