The Catalog File, which stores all the file and directory records in a single data structure, results in performance problems when the system allows multitasking, as only one program can write to this structure at a time, meaning that many programs may be waiting in queue due to one program "hogging" the system. It is also a serious reliability concern, as damage to this file can destroy the entire file system. This contrasts with other file systems that store file and directory records in separate structures (such as DOS's FAT file system or the Unix File System), where having structure distributed across the disk means that damaging a single directory is generally non-fatal and the data may possibly be re-constructed with data held in the non-damaged portions.