Define a SYSMDECK file if you use the MDECK compiler option.
//SYSMDECK DD DSNAME=dsname,UNIT=SYSDA
The SYSMDECK file will contain the output from library processing, that is, the expansion of COPY, BASIS, REPLACE, and EXEC SQL INCLUDE statements. The file can be a traditional MVS data set or an HFS file.
related references
MDECK