To learn how to change preferences, see Changing preferences.
The ElementMatchRule preference specifies which rule Rational Rhapsody DiffMerge will apply to match the elements within the units being compared.
Select Default if you want Rational Rhapsody DiffMerge to try to match elements by ID if there are not matches by name. This means that Rational Rhapsody DiffMerge will be able to detect and report if an element has been renamed and has a different name on each comparison side.
Select Without Renaming Support if you want Rational Rhapsody DiffMerge to match elements only by name. This means that two of the same elements in the same units (in the two Rational Rhapsody projects you are comparing) will never be matched because they have different names.
To see an example of how you might use this preference, see Rational Rhapsody DiffMerge match method.
The ResolveAutomaticallyWhenStartingMerge preference specifies whether Rational Rhapsody DiffMerge must or must not resolve all trivial differences when doing a merge in a base-aware comparison
The Do you want to automatically merge trivial differences? message displays every time until a user selects Use my current reply as default. After that, Rational Rhapsody DiffMerge will or will not resolve differences automatically without asking a user, for example, not displaying that message any more.
The ShowDMMarksinBaseAwareMode preference specifies what Rational Rhapsody DiffMerge displays as the legacy difference and merging state marks when doing a base-aware comparison.
To see an example of how you might use this preference, see Results displayed for compare of three units.