Inventor 2009+ included a couple new sketching constraint suppression tools that have been giving some users a hard time. Constraints are normally applied as you sketch. This process involves the inference and persistence of the constraints. The use of these commands allows users to turn off this functionality and was originally requested by advanced users. This has come up enough in questions and troubleshooting for new or casual users enough that I wanted to take some time and discuss it here.
Inference On - Persistence On
Geometry is created normally with constraint glyphs, tracking, and geometric constraint creation based on options set in the constraint options dialog. The constraint options dialog is activated by right clicking in your sketch and selecting it. The options there should be for all the constraints you want created automatically.
Inference On - Persistence Off
Geometry is created with the aid of constraint glyphs and tracking but geometric constraints are not added with the exception of the Coincident constraint which still has to be turned off manually in the constraint options dialog. This is done to help ensure open profile sketches do not inadvertently get created.
Inference Off - Persistence Off
Sketching is free form and no constraint glyphs, tracking or geometric controls are added to the sketch. You might as well be in AutoCAD. Again the only constraint that is maintained here is the coincident to help avoid open loop sketches.
Leave them on - If you like the idea of the option of not creating certain types of constraints during sketching you can still use a shortcut key to temporarily disable them. While you are sketching hold the CTRL key and it will not add the geometric constraint while sketching your selections. Coincident will still work no matter what.
Remove them - Consider moving these two items to your expanded panel so that you do not inadvertently create a problem for yourself. If you are using 2009 or are still in denial in 2010 using the Classic UI you could remove them from your standard toolbar, but it becomes more difficult to troubleshoot problems when you do this.
Until next time, may your constraints be persistent.