Read about indicating a volume threshold for your applications.
One thing to consider when writing to optical media is the possibility of reaching the media capacity or threshold. The optical file system provides a logical threshold capability to help applications protect themselves from reaching the absolute volume capacity. The logical threshold is defined when the volume initializes, and is unique for each volume. You can change this threshold by using the Change Optical Volume command.
The logical volume threshold is only applicable for high performance optical file system (HPOFS) media format. For UDF media format, the logical volume threshold is always 100% and cannot be changed.
The volume threshold is provided to allow applications to prepare for an actual volume-full condition. When WORM media becomes full, there can be no further write operations. Depending on the requirements of the application, the threshold can be used in various ways to prepare for the media becoming physically full.
For example, an application might write groups of spooled files to optical disk. After each group is written, an additional file might be written that contains an index to the spooled files just written. Without the index, the spooled files could be useless. Unless the application can manage the media capacity, the volume might run out of space before the index file can be written. One way to avoid running out of space is to set the volume threshold to 99%. When the message No space available is issued, the application can then increase the threshold to 100% and write any necessary additional files.