The Meaning of Riwayah and Dirayah
"Riwayah" and "dirayah" - riwayah is transmission and memorization, so it is said "so-and-so is a person of riwayah," meaning from the people of transmission, memorization, precision, and mastery; the "people of dirayah" are the people of understanding and fiqh. Both groups have their own ranks, each according to what Allah has granted him in transmission and in understanding. A person should strive fully in both - memorizing hadith is one thing, knowing its underlying flaw ('illah) is another. If someone combines memorization and knowledge of the flaw, he is called "a person of riwayah and dirayah." If someone has only memorization of hadith without fiqh understanding, he is called "a person of riwayah" - meaning one of precision in preserving the text. He may have some knowledge too, and be called a person of dirayah as well - there's no issue with that. But if he doesn't combine both, and only has riwayah, he still needs dirayah - precision regarding the underlying flaw, and precision in fiqh - to be "a person of riwayah and dirayah."
There may be a person of dirayah without riwayah, like a jurist who is not a hadith scholar - he is called "a person of dirayah," not "a person of riwayah," because he does not narrate with a chain, nor distinguish between authentic and weak hadiths - so he is said to be from the people of dirayah, not riwayah. That's it.