This question already has an answer here:
I have a SharePoint list having more than 2,00000+ records. Its an email enabled list. I got a requirement to move items which are of DateModified > 60 to another list having the same template in another site collection.All the items are having attachments, so i couldn't find a way to batch insert items to the target list keeping attachments using ProcessBatchData method. I am currently iterating through the source items and inserting it in the target and it takes enough time to complete operation for some 5000 items. Could you please help if you know any better way to handle this situation.