void clear(){
  records.clear();
  storedEntries=0;
  storedEntriesPos.clear();
  memoryUndo=0;
  if (file != null) {
    file.closeAndDeleteSilently();
    file=null;
    rowBuff=null;
  }
}

void clear ( ) { records . clear ( ) ; storedEntries = 0 ; storedEntriesPos . clear ( ) ; memoryUndo = 0 ; if ( file != null ) { file . closeAndDeleteSilently ( ) ; file = null ; rowBuff = null ; } }
clear the undo log . this method is called after the transaction is committed .
