New in SolidWorks 2012, feature freeze gives control of these updates to the user. Designs can be frozen in time and locked so that they never require updates. Additional features can be added safely with the knowledge that minimal update time is required to edit and work on the design.
By default, feature freeze is not enable automatically upon installation of SolidWorks 2012
To enable feature freeze option:
Go to Tools > Options > System Options > General > Select Enable Freeze bar > Click OK.
The yellow freeze bar appears at the top of the Feature Manager design tree.
Feature freeze allow you to exclude features from rebuilds of the model. The freeze bar controls the point at which a part's FeatureManager design tree rebuilds. Features above the freeze bar are frozen- you cannot edit them, and they are excluded from rebuilds of the model. Freezing a portion of a model can be useful if you work with complex models with many features. Freezing the features helps to :
• Reduce rebuild time
• Prevent unintentional changes to the model
More information about feature freeze?