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# Using Registration and Existence Checking

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When you register an object with the unit of work, TopLink runs an existence check to determine whether or not the object exists. TopLink uses this information at commit time to determine whether to perform an insert or an update operation. You can specify the default existence checking policy for a project as a whole (see "Configuring Existence Checking at the Project Level") or on a per-descriptor basis ("Configuring Cache Existence Checking at the Descriptor Level"). By default, TopLink uses the check cache existence checking policy. If you use any existence checking policy other than check cache, then you can use the way you register your objects to your advantage to reduce the time it takes TopLink to register an object.

This section explains how to use one of the following existence checking policies to accelerate object registration:

- Check Database

- Assume Existence

- Assume Nonexistence