The OPEN macro can open a z/OS UNIX file specified with the PATH keyword or an MVS™ data set specified with the DSN keyword. The macro supports DD statements that specify the PATH parameter only for data control blocks that specify DSORG=PS (EXCP is not allowed). DFSMSdfp supports BSAM and QSAM interfaces to these types of files:

• Regular files
• Character special files (null files only)
• FIFO special files
• Symbolic links

You cannot open directories or external links.