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# Conflict resolution

Detect and resolve conflicts that occur when data is changed on multiple threads.

## Topics

### Conflict Management

[`NSConstraintConflict`](/documentation/CoreData/NSConstraintConflict)

An encapsulation of conflicts that occur during an attempt to save a managed object.

[`NSMergeConflict`](/documentation/CoreData/NSMergeConflict)

An encapsulation of conflicts that occur during an attempt to save changes in a managed object context.

[`NSMergePolicy`](/documentation/CoreData/NSMergePolicy)

A policy object that you use to resolve conflicts between the persistent store and in-memory versions of managed objects.

[`NSQueryGenerationToken`](/documentation/CoreData/NSQueryGenerationToken)

A token that indicates which generation of the persistent store is being accessed.


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