The JOINKEYS subtasks DO NOT have access to the JPn parameters. Only the main task has access. The main tasks and subtasks DO have access to the SYMNAMES data set.
I see it has already been suggested that you set up a SYMNAMES data set with the JPn symbol as a symbol statement and pass that SYMNAMES data set to the JOINKEYS step. You could use a DFSORT/ICETOOL job something like this:
// SET VOL1=SCRTC1
//SUSYM EXEC PGM=SORT,PARM='JP6"&VOL1"'
//SYSOUT DD SYSOUT=*
//SORTIN DD *
RECORD
//SORTOUT DD DSN=&&S1,UNIT=SYSDA,SPACE=(TRK,(1,1)),DISP=(,PASS)
//SYSIN DD *
OPTION COPY
INREC BUILD=(C'JP6,''',JP6,C'''',80:X)
//S1 EXEC PGM=ICETOOL
//SYMNAMES DD DSN=&&S1,DISP=(OLD,PASS)
//TOOLMSG DD SYSOUT=*
//DFSMSG DD SYSOUT=*
//IN1 DD DSN=... input file1
//IN2 DD DSN=... input file2
//OUT DD DSN=... output file
//TOOLIN DD *
COPY JKFROM TO(OUT) USING(CTL1)
//CTL1CNTL DD *
JOINKEYS F1=IN1,FIELDS=(1,5,A)
JOINKEYS F2=IN2,FIELDS=(1,5,A)
REFORMAT FIELDS=(F1:11,5,F2:21,5,F1:81,6)
OPTION COPY
/*
//JNF1CNTL DD *
INREC IFTHEN=(WHEN=INIT,
BUILD=(1,80,JP6))
/*
I would NOT recommend using SYMNOUT for SYMNAMES since it has the wrong attributes (FBA/121 instead of FB/80). But if you do use the SYMNOUT data set, you'll have to copy it and modify it to have the correct attributes as well as the correct symbols.
