Write-once recording is an irreversible process that uses heat from a laser beam to make holes in the surface of the optical disk. Once the record is created, it cannot be altered. If the data needs to be written again, a new record is created, but the space used by the original entry is not recovered. This type of media is advantageous in instances where a permanent record is needed (for example, signed application forms), or when data is stored that will never be altered or updated (for example, in the case of items being stored on microfiche, completed forms, or X-rays). Because of the permanent nature of the data recorded, you can access WORM optical disks an unlimited number of times (read-many). See Figure 1 for a graphical depiction of WORM recording technique.

Figure 1. Write-Once, Read-Many (WORM) Recording Technique