The AVR32DA28/32/48 devices have a special 32-byte memory section called the User Row (USERROW). The USERROW can be used for end-production data and is not affected by chip erase. It can be written by the Unified Program and Debug Interface (UPDI) even if the part is locked, which enables storage of final configuration without having access to any other memory. When the part is locked, the UPDI is not allowed to read the content of the USERROW.
The CPU can write and read this memory as a normal Flash. Refer to the System Memory Address Map for further details.