4th Dimension will then look in the directory that contains the structure file for a data file with the same name. If 4th Dimension finds the data file, it will open it automatically.

If the data file is not in the same directory or is missing, 4th Dimension displays the Select Data File dialog box. Open the data file by doubleclicking its filename or by selecting the filename and clicking Open.

If you want to specify a different data file or create a new one, click the icon located beneath the Data file area. Clicking this icon opens the Open Data File dialog box.

The data file chosen or created will become the default and will open automatically the next time you open the database.

Opening a Different Data File

You can prevent 4th Dimension from opening the default data file automatically.

To open a different data file:

1 Choose Open > Data File... in the File menu of 4th Dimension.

OR

Hold down the Alt key (Option key on Macintosh) while opening any structure file.

OR
In the Welcome dialog box, click the icon under the Data File area.
4th Dimension displays the Open Data File dialog box.

2 Double-click the desired data file name or select the data file and click Open.

Opening a New Data File

You can also create a new data file by preventing 4th Dimension from opening the default data file automatically.
To create a new data file:

1 Choose New > Data File... in the File menu of 4th Dimension.

OR

Hold down the Alt key (Option key on Macintosh) while opening any database and click the New... button.

OR

In the Welcome dialog box, click the icon under the Data File area.

2. In the Open Data File dialog box, click the New... button.

4th Dimension displays a create-file dialog box.

In the File name text area, 4th Dimension automatically enters a name for the new data file based on the name of the current structure file. 

3. If you wish to enter a new name for the data file, type the name in the File name area then click Save.
The names of any other data files in the directory are displayed. If you enter the name of an existing data file, 4th Dimension displays a message asking you if you want to replace the existing data file with the new data file.

4th Dimension will “remember” where the data file is from then on (4th Dimension stores the pathname of the data file). The Open Data File dialog box will not be displayed again unless you call it intentionally
(as described above), move the data file to a new location, or change its name.

If you are creating a data file that may become very large, you may need to segment the data file. You need to segment a data file if:

 The data file will not fit on your hard disk,

 The data file will become larger than 2 gigabytes.

Using data file segmentation, you can store a single data file on two or more volumes. Each segment can grow to a maximum of 2 gigabytes.
The maximum size of a 4th Dimension data file is 128 gigabytes. You do not need to segment a data file when you first create it. You can wait until it becomes too large to manage on your hard disk.