The D flat dominant ninth chord is a 5-note chord consisting of the notes Db, F, Ab, Cb and Eb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Db9.
Chords that are a superset of Db9. The chords include more notes but always Db, F, Ab, Cb and Eb.
Chords that are a subset of Db9. These contain less notes but all of them are included in Db9.
In case you prefer a non-interactive variant of the chord chart, we've embedded a PNG image below that shows the notes for the the Db9 chord. Feel free to save or share the image as needed.