Use IndexDefs property to read or maintain indexes definitions. 

The dataset also has Indexes collection. Application should use either IndexDefs, either Indexes, but not both in the same time. We suggest to use Indexes, as it is more flexible. IndexDefs property at first is needed for compatibility with other software using TDataSet, where IndexDefs is really defined. 

The TADTable will automatically fill IndexDefs by database indexes, if fiMeta in FetchOptions.Items.

property IndexDefs: TIndexDefs;

Sorting Records, Indexes, TADFetchOptions.Items