300000+ records user importing problem I’m trying to imports data from vBulletin into Drupal using this dev module vbtodrupal
But because the database is too large I experienced a difficult to import ALL data to drupal DB , I discovered that there is a specific limit to importing  is 300k user  ! I searched in google and found that there was a problem with "300000+ records user"

I hope to help . I did not find the response from the support module :(
For an import of that size you will need to run the import in the background and in steps.

This will use cron to run the feeds cron job. Drupal uses a poor-mans cron so it would be best to setup a cron on the server or use a module like Elysia cron. If you do not not you could try something link https://www.pingdom.com (you can use a free account) to ping your site every e.g. minute to trigger the drupal corn.

I would also make sure that your server is optimal for Drupal 7 and just for the import consider increasing php memory limit and execution timeout value.

Nevertheless I would recommend using a more generic module like "Migrate", though it needs some more work to be done.

I personally imported 23K user profiles into Drupal a few months ago, so it is possible.