Migrations into OneDrive/SharePoint – Known Limitations

Here are known issues when migrating content into OneDrive and SharePoint. Folders or files affected by either of these known issue may be NOT be migrated. Content sources that exceed the below limitations will have to be modified prior to the content being migrated into OneDrive and or SharePoint.

Folders containing 10,000 or more items. 

LIMITATION: No single folder can contain more than 10,000 files or folders.

PREVENTION: Before migrating content from file system, rearrange your files so a single folder contains less than 10,000 items (files or other folders).

REMEDIATION: If a migration fails to complete due to too many files in one folder users will need to remediate the source content by moving items into sub-folders until each directory contains less than 10,000 items.

Recommendations:  Account owners should walk through the sub-folders to locate any folder which contain > 10,000 documents/subfolders and rearrange them into other folders.   There can be more than 10,000 files under a parent folder but no single folder can contain more than 10,000 files/folders.

File paths with more than 400 characters

LIMITATION: A file systems being migrated into OneDrive/SharePoint cannot contain more than 400 characters in the folder path (after the folder path is decoded into a URL).

PREVENTION: Before migrating content from a file system, shorten the names of files and folders and avoid using spaces or special characters which are decoded into addition characters that count against the 400-character limit. 

For example, if the file URL in SharePoint is:

https://nuwildcat.sharepoint.com/sites/test/Shared Documents/Promotion Materials/Book&and$and@and.xlsx

The URL is decoded into this: https://nuwildcat.sharepoint.com/sites/test/Shared%20Documents/Promotion%20Materials/Book%26and%24and%40and.xlsx

REMEDIATION:  Rename files and folders using shorter names avoiding spaces or special characters.

Avoid getting throttled or blocked in SharePoint Online

What is throttling?

SharePoint Online uses throttling to maintain optimal performance and reliability of the SharePoint Online service. Throttling limits the number of API calls or operations within a time window to prevent overuse of resources.

User Throttling

Throttling limits the number of calls and operations collectively made by applications on behalf of a user to prevent overuse of resources.

That said, it's rare for a user to get throttled in SharePoint Online. The service is robust, and it's designed to handle high volume. If you do get throttled, 99% of the time it is because of custom code, such as custom web parts, complex list view and queries, or custom apps users run. That doesn’t mean that there aren’t other ways to get throttled, just that they’re less common. For example, one user syncing a large amount of data across 10 machines at the same time could trigger throttling.

Below is a quick summary of the best practices to handle throttling:

• Reduce the number of concurrent requests
• Avoid request spikes
• Choose Microsoft Graph APIs over CSOM and REST APIs when possible
• Use the Retry-After and RateLimit HTTP headers
• Decorate your traffic so we know who you are (see section on traffic decoration best practice more on that below)

More details on SharePoint and OneDrive throttling from Microsoft Learn ==> Avoid getting throttled or blocked in SharePoint Online and Microsoft Graph service-specific throttling limits - Microsoft Graph | Microsoft Learn