Repairing a memory device

A technique includes during in-service use of a memory package in a computer system, using a first interface to access a defective address memory of the memory package. The defective address memory is accessible by a manufacturer of the memory package prior to the in-service use using a second interface of the memory package other than the first interface. In connection with the in-service use of the memory package, the memory package is repair, a repair that includes storing a defective address in the defective address memory to change an address mapping for at least one cell of the storage array.