Do I Have to Delete last batch of data before POST next batch to an import?

Hi all,

I'm coding an integration with Bulk APIs to import Contacts data into Eloqua.

Because of a capacity greater than 32MB, I have to split the data into several batches. Then, I would POST an import for Contacts, and POST data of Batch_1 to the import.

After syncing data of Batch_1 succeeded, I would POST Batch_2 and Sync it.

Here is my question: what would happen about Batch_1? Would it be synced again? Do I have to delete it before POSTing Batch_2?

Thanks,

Biao