Delphi Xe5 firedac Database locked error with SQLite database

Question

I am trying to create a simple object to handle all my database related functions. I have a functions to return a dataset or to execute a command. Now when i call this from my program I am able to fetch records using Execute_Dataset and it works fine but when i do an changes and execute a command by calling Execute_Command i get an error "database is locked" when the commit transaction is called. I have tried everything that i could be it still happens. Can someone put some light into what i am doing wrong and how i can prevent this from happening.

  function TConnectionManager.Execute_Dataset(const ASql: string; const AParams:
      array of variant; out VDataset: TDataset; const ATrn_Name: string): Boolean;
  var
    lTrn: TFDTransaction;
    lQry: TFDQuery;
  begin
    Result := True;
    lTrn:= TFDTransaction.Create (Self);
    try
      lTrn.Connection := FConnection;
      lTrn.StartTransaction;
      lQry := TFDQuery.Create (Self);
      lQry.Connection := FConnection;
      lQry.Transaction := lTrn;
      try
        if Length (AParams) > 0
        then lQry.Open (ASql, AParams)
        else lQry.Open (ASql);
        VDataset := lQry;
        Result := True;
        { Commit transaction if started within the procedure }
        lTrn.Commit;
      except
        on e:Exception
        do begin
           { Rollback transaction if started within the procedure }
           lTrn.Rollback;
           lQry.DisposeOf;
           //log
           raise;
        end;
      end;
    finally
      lTrn.DisposeOf;
    end;
  end;



 procedure TConnectionManager.Execute_Command(const ASql: string; const AParams:
      array of variant; const ATrn_Name: string);
  var
    lTrn: TFDTransaction;
    lQry: TFDQuery;
  begin
    lTrn:= TFDTransaction.Create (Self);
    try
      lTrn.Connection := FConnection;
      lTrn.StartTransaction;
      lQry := TFDQuery.Create (Self);
      lQry.Connection := FConnection;
      lQry.Transaction := lTrn;
      try
        { Execute command }
        if Length (AParams) > 0
        then lQry.ExecSQL (ASql, AParams)
        else lQry.ExecSQL (ASql);
        { Commit transaction if started within the procedure }
        lTrn.Commit;
      except
        on e:Exception
        do begin
           { Rollback transaction if started within the procedure }
           lTrn.Rollback;
           //log
           raise;
        end;
      end;
    finally
      lQry.DisposeOf;
      lTrn.DisposeOf;
    end;
  end;

Thanks

Answer 1

Try setting the Connection's properties SharedCache to 'False' and LockingMode to 'Normal'.

The default value for the connection's locking mode is 'exclusive' which can cause this problem. You can do this by right clicking on your Connection-Component (on the form) and choosing ConnectionEditor (I'm not quite sure, if that's the right English word for it, but it should be called something like that) and then setting these values.

Alternatively you can set these properties in sourcecode:

connection.Params.Add('SharedCache=False');
connection.Params.Add('LockingMode=Normal');

I'm not sure that this is the best way to solve this problem. There might be a better solution to this.

Answer 2

Because other connection exist. Check connection component in datamodule MyFDConnection.Connected:=False;

Answer 3

Sharedcache = false is indeed the best way to solve this problem. The components already support designtime connections.