When you make changes to a database model, those changes are only made in memory. You need to do an explicit call to the commit() method before the changes are stored in the database.

//First decode the model
ILcdModelDecoder decoder =
    new TLcdCompositeModelDecoder(TLcdServiceLoader.getInstance(ILcdModelDecoder.class));
ILcdModel model = decoder.decode(sourceName);

//Make a change: in this example we remove an element
try (TLcdLockUtil.Lock writeLock = TLcdLockUtil.writeLock(model)) {
  Object firstElement = model.elements().nextElement();
  model.removeElement(firstElement, ILcdModel.FIRE_LATER);
} finally {

//Save these changes in the database
try (TLcdLockUtil.Lock writeLock = TLcdLockUtil.writeLock(model)) {
  ((TLcdDatabaseModel) model).commit();