You may use ASMLANGX to create the extract files as sequential files on z/OS, but normally you create a PDS to contain the extracted data for actually debugging the target program using IDF's Language Support.

   RECFM(VB) LRECL(1562) BLKSIZE(27998)

Memory above the 16 MB line is exploited for extract information.

ASMLANGX does not perform any dynamic allocation. You will need to allocate the SYSADATA data set to DDname SYSADATA and the ASMLANGX data set to DDNAME ASMLANGX before you invoke the ASMLANGX command processor.