https://www.ibm.com/docs/en/ims/15.1.0?topic=dfsddlt0-sysin2-dd-statement
IMS 15 - Application programming APIs - SYSIN2 DD statement
DFSDDLT0 does not require the SYSIN2 DD statement, but if it is present in the JCL, DFSDDLT0 will read and process the specified data sets.
application programmingimsapisddstatement