Which file system is used for Optical Media?

ISO9660 file system also referred to as CDFS (Compact Disc File System)

Writable optical media (such as WORM, erasable, DVD-RAM) is initialized on i5/OS using the Initialize Optical (INZOPT) command. WORM media must use the High Performance Optical File System (HPOFS) format. DVD-RAM media must use Universal Disk Format (UDF). Erasable media can use either HPOFS or UDF depending on the requirements of the user. You can specify the format by using the MEDFMT keyword on the Initialize the optical volume (INZOPT) command. 

http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp?topic=/com.ibm.aix.baseadmn/doc/baseadmndita/fsoptical.htm

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