In general, when we create sketch pattern for simply sketch geometry is not get fully defined. Sketch in feature tree contain symbol of under define (-) as shown in the below image. And this happen even after instance that use for pattern is fully defined.
These issue of under defined sketch pattern is occurs because of unselected option of “Dimension X spacing”, “Dimension Y spacing” and “Dimension angle between axes” while creating sketch patten. Refer below image for better clarity.
After selecting these options in sketch pattern, SolidWorks will add necessary dimension in sketch to make pattern fully defined. Refer below image for more information.
And now you can see sketch feature in feature tree is fully defined.