A memory medium has a plurality of tracks arranged in a plurality of sectors with each track sector having a format which does not include header fields identifying sectors or sector defects or defect management procedures. Track management apparatus identifies the track sector currently confronting a transducer; the track management being based on sector pulses (in the case of a dedicated servo system), or being calculated based on track information, an index pulse and data wedge information from previous wedges (in the case of embedded servo systems), or being derived from a lookup table. To accommodate sector defects, a defect bank contains the identity and type of each defective or spare sector. Defect management apparatus is connected to the defect bank and track management apparatus to indicate when the sector confronting the transducer is a defective or spare sector to halt data transfer to thereby skip the defective sector, or to generate an interrupt signal to the processor to transfer data between the processor and an alternate sector.