procedure TForm1.BitBtn1Click(Sender: TObject);
var
  FD: TDBISAMFieldDef;
begin
  with tblSongs do
    begin
      TableName := 'WASongs';
      DatabaseName := '';
      if ((UserMajorVersion = 3) and (UserMinorVersion = 0)) then
        begin
          FieldDefs.Update;
          with FieldDefs do
            begin
              FD := Find('USER1');
              if (FD <> nil) then
                FD.Size := 30;
              FD := Find('USER2');
              if (FD <> nil) then
                FD.Size := 30;
              FD := Find('USER3');
              if (FD <> nil) then
                FD.Size := 30;
              FD := Find('ROADMAP');
              if (FD <> nil) then
                FD.Size := 30;
              Insert(23, 26, 'FILELINK1', ftString, 80, false);
              Insert(24, 27, 'FILELINK2', ftString, 80, false);
            end;
          IndexDefs.Update;
          AlterTable (0, 3, 1);
        end;
      if ((UserMajorVersion = 3) and (UserMinorVersion = 1)) then
        begin
          FieldDefs.Update;
          with FieldDefs do
            begin
              FD := Find('ROADMAP');
              if (FD <> nil) then
                FD.Size := 80;
              Insert(25, 28, 'UPDATED', ftDateTime, 0, false);
            end;
          IndexDefs.Update;
          AlterTable (0, 3, 2);
        end;
    end;
end;

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 Comments and Workarounds

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The problem was caused by the second FieldDefs.Update not working properly. The internal TDataSet FieldDefs thought that they didn't need to update after the first AlterTable call even though they did, and subsequently did not cascade an update requirement down to the TDBISAMFieldDefs.

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 Resolution

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Fixed Problem on 1/12/2004 in version 4.02 build 1