3.4 vs ISRDDN when hunting which dataset a member came from

Junior asked how I find which library in a concatenation supplied a member. I muscle-memory ISRDDN and they looked lost.

What do you teach new people first - 3.4, ISRDDN, or something else?

ISRDDN early. Once they see LISTA and the ddnames click, half of "it works on my TSO" tickets go away.

Wish someone had shown me ISRDDN week one. Found a personal STEPLIB shadowing the shop MACLIB.