"Secondary" Rast is a jins that is tremendously common in the repertory--it is the main upper jins for Maqam Rast--but it is unnamed as such in previous theory, which instead refers to the second jins of Maqam Rast as "Jins Rast 5." In my view, this is incorrect, as I discuss on this page. (See also the discussion in the article "Maqam Analysis: A Primer.") The use of two numbers in identifying the tonic of the Jins ("2nd Rast 5/8") indicates the traditionally assigned tonic (5), which is the starting point of the jins, and the actual tonic (8), which is the note of emphasis and resolution; this distinction is elaborated below.
Compare the following examples: #01 from Muwashshah "Ya Shadi il-Alhan":
#01 from Muwashshah "Sihtu Wajdan":
#01 from Ya Maal ish-Sham
#05, #07, #09 & #11 from Hayrana Leh
From Aruh Li Meen, #02, #51, #54 & #57
In all of these cases, it is easy to hear that the jins in question doesn't tonicize the fifth scale degree of the Maqam, but rather the 8th scale degree (the octave). If this jins were really "Jins Rast on 5" we would also expect to hear the typical jins baggage underneath Jins Rast--which would modify the 3rd and 4th scale degrees, similar to the modification underneath Jins Rast when it occurs as a secondary Jins elsewhere (hear examples)
Fakkaruni, an Umm Kulthum song composed by Mohamed Abdel-Wahhab, offers the only real counter-example in the repertory, in which the 5th scale degree, (rather than the 8th) is really tonicized, and the expected modifications to scale degrees 3 & 4 do occur; listen to #13:
In fact, the usual Jins "Secondary Rast" even occurs as #16 in the previous example; by comparing it with #13 it is plain to see the two are different melodic entities, hence different Ajnas. See the full discussion of Fakkaruni on the Unique Pathways page.
Jins Secondary Rast is also used prominently in Maqam Sikah, whose principal secondary jins is Jins Rast on the 6th scale degree. Previous theory mistakenly claims that Maqam Sikah uses Jins Rast on the 3rd scale degree, and this mistake is identical to the mistake involving Jins Rast on the 5th scale degree of Maqam Rast. What does occur on the third scale degree of Maqam Sikah is "Jins Secondary Rast," leading up to and tonicizing the 6th Scale degree.
Listen to examples from the Sikah Muwashshah "Jadaka-l-Ghaithu", #08, #10, #12, #14, #18: