Disk at once recording will write a complete disk in one stage. By doing this, no space is wasted between tracks, but also all data has to be generated before writing to the disk starts. Thus lead in and Table of Contents must be known, along with ever sector location that will be used. The safest way to generate this type of disk is to produce an image on the hard drive first, and then write the disk. The write laser is never turned off in this process.
Because of the fixed table of contents, only a single session may be written, and the disk is therefore closed at the end, and no further data may be appended. The process is very useful when producing a master disk that will be used for pressing. When the data is written, the laser is never turned off. It could be argued that it makes it a very reliable method of writing, but there is no flexibility about adding extra sessions.
Disk at Once is often used to produce master disks for mass production, and is typically used for audio disks.
When possible CnW Recovery software will log the disk mode in the status part of the log.