As per Hindu astrology, when all the seven planets, except Rahu and Ketu, occupy one house, each beginning from lagna (first house, consecutively, Vallaki Yoga comes into being. Vallaki Yoga or Vina Yoga is a favorable yoga and the person will have a large number of friends; he will be fond of music and fine arts; and will be learned, happy and famous.
This yoga is the first of Samkhya Yoga caused by numerical combination. All the seven planets – Sun, Moon, Mars, Venus, Jupiter, Mercury and Saturn – should be found in any seven signs (one in each sign), beginning with lagna.
Varahamihira has dealt with special yogas called Nabhasa Yoga in his Brihat Jataka, and Vallaki Yoga is one of the sub-categories of Yogas called Samkhya Yoga.
It is also seen that Samkhya Yoga sometimes actually coincides with the other sub-category of Nabhasa Yoga called Akriti Yoga. In such cases, Samkhya Yoga – including Vallaki Yoga – loses its individuality, and in those conditions they may not be studied separately.
It may be noted that Nabhasa Yoga are 32 in number and their subdivisions are Akriti Yoga (20), Samkhya Yoga (7), Asraya Yoga (3) and Dala Yoga (2). Vallaki Yoga is one of them.
Some texts, however, differ in the definition of Vallaki Yoga but not in the results.
According to them, all the seven (major) planets should occupy the seven houses from lagna and not necessarily consecutively. Thus, even if there are some planetless houses in between, it does not matter, as long as seven planets are housed in only seven signs. Vallaki Yoga is a positive and favorable Yoga.
Source – Three Hundred Important Combinations by B.V. Rama (1997) published by Motilal Banarsidass.
Astrology For You By Shakuntala Devi (1985) Orient Paper Books Delhi.
Encyclopedia of Hinduism Volume XI IHRF page 528 to 529