Hi Guangming,
The detection jobs, both in cRM 4 and CRM 2011 cannot delete duplicates automatically, this is normally a manual process, by design for security purposes.
The impact of the associated records when you delete the duplicate, will be decided based on the relationships they have between each other.
Parental
Referential
Referential, restrict delete
If you have custom entities that may get associated with records that can be potentially deleted in mistake, you can set a relationship which prevents a deletion from deleting the associated records as well. e.g. the parental relationship will delete all
associated records.
The following article is very helpful:
http://info.profad.com/bid/79553/Microsoft-Dynamics-CRM-2011-Relationship-Behavior
Regards
Nuno
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