JCL contains syntax :

 JOINKEYS FILE=F1,FIELDS=(1,3,A)
 JOINKEYS FILE=F2,FIELDS=(1,3,A),SORTED
 REFORMAT FIELDS=(F1:1,112)
 SORT FIELDS=(1,3,PD,A)

When run the job fails with the error :

"SORTJNF2 (F2) KEY IS OUT OF SEQUENCE"

Full article: https://portal.microfocus.com/s/article/KM000015588