Root Dictionaries
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§Two Root dictionaries
§Named Objects Dictionary (NOD)
Owned by the database
Available by default
Used to store database level data
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§Extension Dictionary
Owned by an Entity
Created by the user only when needed
Used to store entity level data
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§Use ARXDBG to look where the dictionaries are stored
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If you examine the database of brand new drawing you will find that a dictionary is automatically created. The name of this dictionary is the Named Objects Dictionary. Commonly referred to as the NOD. This dictionary will contain other dictionaries. You can think of it as the root dictionary for the drawing and it is used to store data  at the database level. There is another type of dictionary that can be created. It is called an Extension dictionary an it can exist for any Entity in the drawing. You use the extension dictionary to store data with that entity. This dictionary is only created by a custom program and does not exist by default.  Lets use our MgdDBG example to see the dictionaries in the AutoCAD drawing database.