FIELD: digital data recording on and reproducing from mirror disk. SUBSTANCE: writable and/or rewritable record medium includes initial domain, final domain, and user's data domain. Record medium saves write protection information capable of protecting data recorded on data medium against unwanted record superposition or erasing, write protection information being saved as backup information in plurality of initial domain locations. As an alternative, initial domain is provided in addition with disk identifying area. As one more alternative, write protection information is saved as backup information in plurality of initial domain locations, record medium being writable/reproducible record medium complying with multipurpose digital disk specifications. EFFECT: provision for protecting case-residing disk against unwanted records. 13 cl, 20 dwg, 2 tbl
