NexusDB

In version 2, it is now possible to have several logical tables within one physical file. This is implemented in the data dictionary by being able to create a tree-structure of table descriptors. Each table descriptor contains all other descriptors needed for that particular table, and an array of child table descriptors. Simplified, the structure looks like this for a table with children:

TableDescriptor (Rootnode/main table)

  Autoinc Descriptor

  FieldsDesscriptor

  IndicesDescriptor

  ...other descriptors

  TablesDescriptor (array)

     TableDescriptor (child 1)

        Autoinc Descriptor

        FieldsDesscriptor

        IndicesDescriptor

        ...other descriptors

        TablesDescriptor (array)

   ...

     TableDescriptor (child n)

        Autoinc Descriptor

        FieldsDesscriptor

        IndicesDescriptor

        ...other descriptors

        TablesDescriptor (array)

It is important to note that in NexusDB, transaction granularity is on physical files, not the logical tables. You should therefore only use childtables if you are regularly going to include the logical tables in a physical file in the same transaction. If different transactions would update different logical tables in the same physical file, then this will likely cause slowdowns due to transactions not being able to execute in parallel.

The Enterprise Manager shows a graphical view of this structure when creating and restructuring tables.