A single segment data structure and method for storing data objects employing a single segment data object having a header and a data record. The header includes a segment length field describing the length of memory reserved for the data record and the data record contains at least one data instance object. Each of the data instance objects has a data instance header and data field. The header includes a data instance state field and a data instance length field. The data instance length field contains data representing the length of the data instance data field allowing for variable length "in place" updating. The data instance state field contains data representing an object state of the instance data. Only one of the data instance objects of the data record of the single segment data object has a valid object state. The state field facilitates a power loss recovery process.