Concerns Regarding SharePoint/OneDrive Reliability and Potential Data Integrity Issues

Dear @Zsófia Dicenty, 

Good day, and I appreciate the clear explanation of your concern. 

Please refer to the following information to clarify what these behaviors typically mean and how they relate to your concern about possible data integrity issues. 

In Microsoft 365, Excel sync conflicts and inconsistencies usually don’t mean there’s a serious data integrity issue in SharePoint or OneDrive. They happen when the system detects multiple changes it can’t safely merge, so it pauses syncing and asks for manual resolution to avoid overwriting data. This is expected behavior, the main risk is losing recent edits if conflicts aren’t handled carefully, not file corruption or system instability. 

• Cause of this issue in your environment: 

1/ Concurrent editing across multiple users 

When several users edit the same workbook at the same time, especially across different applications or devices, the system may not always be able to merge all changes seamlessly. 

2/ Complex workbook structure with cross file links 

Workbooks that reference other files introduce additional dependencies. If one file is updated, out of sync, or saved at a different time, it can create inconsistencies that propagate across connected workbooks. 

3/ Dependence on sync and network conditions 

AutoSave and synchronization rely on stable connectivity. Any interruption or delay can lead to competing versions of the same file. 

4/ Co-authoring not always fully active 

Certain workbook conditions can limit or block co-authoring without being obvious to users. When this happens, Excel may fall back to less coordinated save behavior, increasing the likelihood of conflicts. 

• Sync conflict vs. file corruption: 

It is important to distinguish between these two scenarios: 

• Sync conflicts occur when there are competing edits, but the file remains usable and opens normally. 
• File corruption typically presents as errors when opening, repair prompts, or data recovery requirements. 

If your files are opening normally and the main issue is conflicting or inconsistent changes, this is not typical of true corruption. 

• How to assess the level of risk: 

You are unlikely to be facing a serious data integrity issue if: 

• Files open normally in SharePoint or OneDrive. 
• Conflicts appear as duplicated or mismatched changes. 
• You can recover correct data using Version History. 

Further investigation may be needed if: 

• Excel frequently reports corruption or requires repair. 
• Multiple versions in history show the same damaged state. 
• Files cannot be opened or reliably used. 
• Multiple files experience one or more recurring issues within a short period of time. 
• Here are some recommended steps to reduce risk: 

1/ Use Version History as a safeguard 

Open the file in SharePoint or OneDrive. 

Select Version History. 

Review or restore a previous stable version when needed. 

This ensures that even if a conflict is resolved incorrectly, earlier versions remain available. 

2/ Handle conflicts carefully 

Select Open to Resolve when prompted. 

Review differences between versions. 

Save the file after confirming the correct content. 

Avoid replacing versions without review, as this may result in lost edits. 

Troubleshoot OneDrive for work or school sync issues - SharePoint | Microsoft Learn 

3/ Improve co-authoring reliability 

Ensure files are in supported formats such as .xlsx or .xlsb.

Always open and edit files directly from SharePoint or OneDrive. 

Avoid working on local copies or using legacy sharing methods. 

4/ Reduce sync related risks 

Keep the OneDrive client updated. 

Avoid editing files while offline. 

Maintain stable internet connectivity during active editing. 

If sync issues persist, you can refer to these steps to troubleshoot the OneDrive app: Fix OneDrive sync problems - Microsoft Support 

The behavior you are seeing is consistent with normal synchronization and collaboration limitations in complex Excel environments, not a system level data integrity issue. 
However, frequent conflicts should be monitored, as they can lead to lost recent changes and confusion across linked files if not handled carefully. 

Additional information is available in the following resources: 
Troubleshoot co-authoring in Office - Microsoft Support 

Repair a corrupted workbook - Microsoft Support 

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Thank you for your patience and understanding. 

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SharePoint and OneDrive in Microsoft 365 are designed with strong data integrity and resiliency mechanisms, but certain usage patterns (especially with complex Excel workbooks and concurrent editing) can still surface sync conflicts and operational issues at the client level. The key points are:

1. Platform-level data integrity and corruption protection

• In Microsoft 365, customer data in SharePoint and OneDrive is stored using a custom solution on Azure Storage where every file is written simultaneously to a primary and a secondary datacenter region. If either write fails, the save fails, preventing partial or inconsistent commits.
• After a file is written, checksums are stored separately with metadata and used on every read to verify that the stored content matches the original file. This helps prevent propagation of corruption through the lifecycle of the file.
• Storage is append-only: new blobs are added, and existing blobs are not modified until they are permanently deleted. This protects previous versions from being altered or corrupted after the initial save and allows retrieval of earlier versions, depending on administrator settings.
• Within each region, Azure Locally Redundant Storage (LRS) provides additional reliability for the stored data.
• For trial or unpaid accounts (for example, unlicensed OneDrive for Business), data might be stored in a single Azure region only, which is a different resiliency profile than fully licensed tenants.

These mechanisms are specifically intended to reduce the risk of platform-level data corruption and ensure that what is stored in the service remains consistent and recoverable.

2. Versioning and recovery capabilities

• SharePoint document libraries default to 500 versions per file for newly created libraries. This can be increased, and it is not recommended to reduce it below 100, because lower values can increase the risk of inadvertent data loss from user activity.
• Files Restore allows going “back in time” for any document library to any second in the last 30 days. This can be used to recover from ransomware, mass deletions, corruption events, or other incidents. Files Restore relies on file versions, so reducing the number of stored versions can reduce its effectiveness.

These capabilities are directly relevant to mitigating the impact of synchronization conflicts or accidental overwrites: if a workbook becomes inconsistent or damaged due to client-side operations, previous versions can be restored at the library level.

3. Sync conflicts and client-side issues

The types of issues described (sync conflicts, inconsistent Excel files, operational problems) often arise from client-side synchronization behavior rather than underlying storage corruption. The documented causes for continuous sync issues in OneDrive/SharePoint include:

• Hitting restrictions or limitations such as:
  • Maximum number of items that can be synchronized
  • File size limits
  • Invalid characters in file or folder names
  • Path length limits for SharePoint/OneDrive
• Files containing links to other files where the link paths are broken by relocation or renaming (for example, PowerPoint or web pages linking to other content). Similar patterns can apply to Excel workbooks with cross-file references if files are moved or renamed.
• Insufficient local disk space on client devices to process sync operations.
• For older versions of the sync client, 0 KB files in the library.
• Local path length exceeding 260 characters from the root drive.

Additionally, sync conflicts can occur when:

• Multiple files are uploaded at the same time via the OneDrive website.
• Changes are made to the same files from different PCs that are syncing concurrently.
• Files are edited offline and then re-synced.

In these cases, conflicts are often resolved by renaming edited files or folders to unique names and saving again, rather than indicating underlying storage corruption.

4. Practical implications for complex Excel usage

Given the platform characteristics and the documented sync behaviors:

• The underlying SharePoint/OneDrive storage is engineered to prevent and detect corruption via dual-region writes, checksums, and append-only storage. This significantly reduces the likelihood of silent, platform-level data corruption.
• The most likely sources of the issues described are:
  • Client sync conflicts when multiple users edit the same workbook concurrently.
  • Broken or outdated cross-file references when files are moved, renamed, or reorganized.
  • Local environment issues (path length, invalid characters, disk space, or older sync client behavior) that cause sync loops or incomplete syncs.
• To mitigate risk of future data loss or instability:
  • Ensure document libraries retain a sufficient number of versions (at least the default 500, and not fewer than 100) to support recovery.
  • Use Files Restore when a library experiences a broad incident (mass corruption, ransomware-like behavior, or widespread inconsistencies) to roll back to a known-good point in time.
  • Review and address documented sync restrictions and limitations (file counts, sizes, naming rules, path lengths) and ensure client devices have adequate disk space and up-to-date sync clients.

These measures align with the built-in resiliency and recovery capabilities of SharePoint and OneDrive and help reduce the operational impact of synchronization conflicts and complex Excel collaboration scenarios.

References:

• SharePoint and OneDrive data resiliency in Microsoft 365
• A OneDrive file or folder never finishes synchronization
• Restrictions and limitations in OneDrive and SharePoint
• Dealing with data corruption in Microsoft 365