Author: Tomas Rutkauskas 

Using D6 Pro, Access XP and Jet 4.0 Sp6 - how can I compact Access files?

Answer:

This does it:
1   
2   procedure TMainForm.ActionCompactAccessDBExecute(Sender: TObject);
3   var
4     JetEngine: Variant;
5     TempName: string;
6     aAccess: string;
7     stAccessDB: string;
8     SaveCursor: TCursor;
9   begin
10    stAccessDB := 'Provider = Microsoft.Jet.OLEDB.4.0;' +
11      'Data Source = %s;Jet OLEDB: Engine type = ';
12    stAccessDB := stAccessDB + '5'; {5 for Access 2000 and 4 for Access 97}
13    OpenDialog1.InitialDir := oSoftConfig.ApplicationPath + 'Data\';
14    OpenDialog1.Filter := 'MS Access (r) (*.mdb)|*.mdb';
15    if OpenDialog1.execute and (uppercase(ExtractFileExt
16      (OpenDialog1.FileName)) = '.MDB') then
17    begin
18      if MessageDlg('This process can take several minutes. Please wait till the end 
19  '+
20        #13 + #10 + 'of it. Do you want to proceed? Press No to exit.', mtInformation,
21        [mbYes, mbNo], 0) = mrNo then
22        exit;
23      SaveCursor := screen.cursor;
24      screen.cursor := crHourGlass;
25      aAccess := OpenDialog1.FileName;
26      TempName := ChangeFileExt(aAccess, '.$$$');
27      DeleteFile(PChar(TempName));
28      JetEngine := CreateOleObject('JRO.JetEngine');
29      try
30        JetEngine.CompactDatabase(Format(stAccessDB, [aAccess]),
31          Format(stAccessDB, [TempName]));
32        DeleteFile(PChar(aAccess));
33        RenameFile(TempName, aAccess);
34      finally
35        JetEngine := Unassigned;
36        screen.cursor := SaveCursor;
37      end;
38    end;
39  end;


Important Notes:
Include the JRO_TLB unit in your uses clause.
Nobody should use or open the database during compacting.
If the compiler gives you an error on the JRO_TLB unit follow these steps:
Using the Delphi IDE go to Project – Import Type Library.
Scroll down until you reach “Microsoft Jet and Replication Objects 2.1 Library”.
Click on Install button.
Recompile a gain.