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The remote server returned an error (429)

Last Update: 7/21/2017 11:32 AM
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​​SharePoint Online or OneDrive For Business returns HTTP status code 429 ("Too many requests") when you are migrating to SharePoint Online or OneDrive For Business using the endpoint type SharePoint or OneDrive For Business. These endpoints use the client-side object model (CSOM) API, which is subjected to throttling from Microsoft. This can result in errors when MigrationWiz exceeds the CSOM API usage limits.



When CSOM API throttling limits are continually exceeded over a long period of time, the SharePoint Online CSOM API will throttle any further requests from MigrationWiz in order to prevent overuse of SharePoint or OneDrive For Business resources. Once the throttle is in effect and a 429 error is returned, MigrationWiz will use an incremental backoff in order to reduce the number and frequency of calls. However, in some cases, MigrationWiz can continue to exceed those usage limits. This results in SharePoint Online completely blocking the migration and returning an HTTP status code 503 ("Service unavailable").

If this occurs, follow the steps in either one of the options listed below:

Option 1:

  • Pause the migration for each item. KB004662
  • Wait for a period of 24 hours.
  • Resubmit each item for migration. Migrations will begin from where they left off, at the time of the pause. KB005332

Note: Option 1 requires that you wait for 24 hours before resubmitting your migration.

 Option 2:

  • Pause the migration for each item. KB004662
  • Edit the project endpoint to use either SharePoint Online v2 or OneDrive Pro For Business v2. KB004629
  • Reset statistics for items. KB005101
  • Remove items from the Destination. Make sure to only remove migrated items. If the user is already using the Destination, make sure that you do not delete any new files that were added by the user.
  • Resubmit each item for migration. KB005332


  • Option 2 allows you to resubmit your migrations immediately.
  • V2 connectors only support one Full Migration pass. You cannot run multiple migration passes, or follow a Pre-Stage Migration strategy, when choosing the V2 connector.
  • To learn more about the V2 connectors, refer to KB005509.
  • If the migration fails, rather than pauses, an additional step for Option 2 is required. Add the following MigrationWiz project Advanced Option, under Support/Support Options, before resubmitting the migration. This is required in order to clean up the metadata database in Azure. KB005100

    • SpCleanUpBeforeMigration=1