writes a setstring record to the log . this log record contains the setstring operator , followed by the transaction id , the filename , number , and offset of the modified block , and the previous string value at that offset . concode_field_sep Block blk concode_elem_sep String oldval concode_elem_sep int offset concode_elem_sep int txnum concode_elem_sep String newval concode_field_sep int op concode_elem_sep void undo concode_elem_sep String toString concode_elem_sep void redo concode_elem_sep int txNumber