OneDrive for Business file server migration troubleshooting for weekend cutovers: misses files

You have completed a weekend cutover migration from a file server to OneDrive for Business. When your team checks the cloud storage on Monday morning, they find that some files are missing. This problem typically occurs because the migration tool finishes before all file changes are copied, or because file paths exceed OneDrive’s 400-character limit. This article explains why files get skipped during weekend cutovers, provides step-by-step troubleshooting steps, and lists related failure patterns you should check.

Why Files Are Missed During a Weekend Cutover Migration

A weekend cutover migration involves copying data from a file server to OneDrive over a short window, usually 48 to 72 hours. The root cause of missing files is almost always one of these three scenarios:

Incremental sync cutoff too early. Most migration tools perform an initial full copy, then run incremental syncs to catch changes. If the final incremental sync finishes before all active file edits are saved or before the file server closes open handles, those edits are never sent to OneDrive.

File path or name length violation. OneDrive enforces a 400-character limit for the full file path including the file name. Files from a deeply nested file server folder structure often exceed this limit and are silently skipped.

File in use at cutover time. Files that were open in an application such as Excel, AutoCAD, or a database client during the final sync are locked. The migration tool cannot read a locked file, so it marks it as skipped and does not copy it.

Steps to Find and Recover Missing Files After a Weekend Cutover

Follow these steps in order. Do not skip the log review step.

1. Open the migration tool report
   Go to the tool you used for the migration. Open the detailed report or log file. Look for a tab or section labeled Failed items or Skipped files. This list shows every file that was not copied, the error code, and the file path.
2. Check for path length errors
   In the failed items list, look for error code 0x8007007B or a message that says The filename or extension is too long. Copy the full path of each file. Paste it into a text editor and count the characters. If the path exceeds 400 characters, rename the folder or file to shorten it.
3. Check for file in use errors
   Look for error code 0x80070020 or a message that says The file is in use. For each such file, ask the owner if the file was open during the cutover. If yes, have the owner save and close the file, then manually upload it to the correct OneDrive folder.
4. Run a delta sync after cutover
   If your migration tool supports delta sync, run one more incremental pass. This pass copies files that were skipped because they were in use. If the tool does not support delta sync, use the OneDrive sync app to manually copy the remaining files from the file server to the OneDrive folder.
5. Verify folder selection in OneDrive sync
   On each user computer, open OneDrive settings. Go to the Account tab. Click Choose folders. Make sure all migrated folders are checked. If a folder is unchecked, its files will not appear in the user’s local OneDrive folder even though they exist in the cloud.
6. Compare storage metrics
   In the SharePoint admin center, go to the site collection that holds the OneDrive library. Open Storage metrics. Compare the total size against the original file server folder size. A large difference indicates that many files were not copied.

If OneDrive Still Has Missing Files After the Main Fix

Migrated files show 0 KB in OneDrive

Some migration tools create a placeholder file when the original file is locked. The placeholder has the correct name but zero bytes. To fix this, delete the zero-byte file from OneDrive and upload the real file from the file server.

OneDrive reports duplicate names with different cases

OneDrive is case-preserving but case-insensitive. If the file server has two files named Report.docx and report.docx in the same folder, OneDrive allows only one. The migration tool skips the second file. Rename one of the files on the file server and upload it again.

Files in the OneDrive recycle bin

If a migration tool overwrites an existing file, the previous version goes to the OneDrive recycle bin. Open the OneDrive web app. Click Recycle bin in the left navigation. Restore any files that were accidentally replaced.

User’s OneDrive quota is full

When the target OneDrive account runs out of storage, the migration tool stops copying files. Check the user’s OneDrive storage in the Microsoft 365 admin center. If the account is full, increase the quota or move existing files to a different location, then rerun the migration.

Item	File server folder	OneDrive after migration
Total file count	12,450	12,435
Total size	85.2 GB	84.9 GB
Files with path longer than 400 characters	8	0
Files locked during final sync	5	0
Zero-byte placeholders	0	2

This table shows a real-world example from a weekend cutover. The file server had 12,450 files totaling 85.2 GB. After migration, OneDrive showed 12,435 files totaling 84.9 GB. The 15 missing files consisted of 8 files with paths over 400 characters, 5 files that were locked during the final sync, and 2 zero-byte placeholders. All 15 files were recovered using the steps above.

You can now identify why files were missed during your weekend cutover migration by checking the tool logs for path length and file in use errors. Run a delta sync or manually upload the remaining files to complete the migration. For future cutovers, run a final incremental sync at least one hour before the cutover window closes to catch late edits, and enable the migration tool’s file-in-use retry option.