SDSF Batch command size limit

[mikexcell]

I would like to submit a batch job to issue a D GRS command. However, I find that the total command exceeds the size that one can issue on SDSF command line. Is there a way to issue a slash in SDSF batch to get to the System Command Extention? I tried but it does not seem to work. I tried program ISFAFD, but it appears to continue with an Enter command. Below is JCL:

//WHOHAS EXEC PGM=ISFAFD
//ISFOUT DD SYSOUT=*
/
D GRS,RES=(SYSDSN,PEQUF.RPTLB.CAVIEWUN.PPOPTION)

I would like to do this in REXX that displays the results. If anyone has a sample pgm, I would greatly appreciate it.