Characteristics of the Sequential Subset Randomizer

The randomizing techniques used by the Sequential Subset Randomizer are an extension of the randomizing techniques used by the standard IMS DFSHDC40 randomizer module.

The Sequential Subset Randomizer maintains (as DFSHDC40 does) the physical RAP sequence of database records through a database reorganization in the following cases:

  • The number of CIs/blocks within the Root Addressable Area (RAA) is changed.
  • The CI size or block size is changed.
  • The number of RAPs per CI/block is changed.
  • The relative amount of space within the RAA allocated to each subset is changed.

A change of these characteristics requires a database reorganization.

With the Sequential Subset Randomizer, as with DFSHDC40, if two different databases have database roots with identical keys, the physical RAP sequence of the database roots will be the same in the two databases.

As DFSHDC40, the Sequential Subset Randomizer supports the formatting of the whole root addressable area through the insertion of a root whose key begins with an X'FF'.