The scales of Shuddha Dhanyasi (Suddha Dhanyasi) are as follows :
Aarohanam (Ascending) : S G2 M1 P N2 S’
Avarohanam (Descending) : S’ N2 P M1 G2 S
It is a janya raga, a pentatonic scale derived from Kharaharapriya (see below) which is 22nd on the Melakarta scale.
Shuddha Dhanyasi has the same notes as Udayaravichandrika of the Dikshithar tradition. Though there are differences in inflections, the two are considered roughly the same. The mood of this raga ranges from deeply devotional, softly soothing to intensely romantic (especially in film music), depending on how it is used.
Some well known compositions in Shuddha Dhanyasi are Narayana Ninna Namada by Purandaradasa, Enta Nerchina by Tyagaraja, Himagiri Tanaye by Muttiah Bhagavathar and Subrahmanyena Rakshitom by Muthuswami Dikshithar.
There is a good discussion on Dhanyasi with mentions of Shuddha Dhanyasi and Udayaravichandrika in this article here.
Tamil readers may enjoy the following discussion on the raga by Charulatha Mani.
Note : The 12 notes in the octave are named as below. Please note that C is used as Sa for the sake of simplicity as the scale is relative in Carnatic Music. Also note that the scales paint only a superficial picture of the raga as the gamakas(ornamentations) are a very important part of a raga.