Parivartan or Anonya Yoga

Parivartan Yoga happens when two planets exchange their rashis. For example, when Lord of Aries (Mars), is placed in Sinha Rashi and Lord of Leo Rashi (Sun) is placed in Aries. 

In this yoga, the two planets support each other. Even if the planets in the yoga are malefic, the effect of the yoga is benefic.