You can position a datum plane by selecting any plane on the model (including another datum plane) and specifying an offset from the selected plane; you can specify the offset by entering a value or selecting a point.
To create a datum plane offset from a principal plane:
From the main menu bar, select Tools
Datum.
The Create Datum dialog box appears. The dialog box outlines the types of datum geometry you can create.
Abaqus/CAE displays prompts in the prompt area to guide you through the procedure.
Tip:
You can also create a datum plane using the 
tool, located in the module toolbox. For a diagram of the datum tools in the toolbox, see “Using the Datum toolset,” Section 62.2.
From the list of types at the top of the dialog box, choose Plane.
The Method list indicates the methods you can use to create a datum plane.
From the Method list, select Offset from principal plane.
From the buttons in the prompt area, select the principal plane.
In the text field in the prompt area, enter the offset from the selected principal plane. The offset can be positive or negative. A positive value offsets the datum plane along the positive principal axis normal to the selected plane.
The datum plane appears. You can modify the position of the datum plane by selecting FeatureEdit from the main menu bar and modifying the value of the offset.
