Error
Error Code:
221
MongoDB Error 221: Unexpected Index Change
Description
This error indicates that the internal state of an index changed unexpectedly during an operation. It commonly occurs when background index operations, such as builds or modifications, conflict with active queries or other administrative commands, leading to an inconsistent view of the index.
Error Message
Index Modified
Known Causes
3 known causesConcurrent Index Operations
Another operation, such as a background index build, drop, or rebuild, modified the index while it was actively being used by another query or command.
Replication Inconsistencies
A replica set member might encounter this error if its index state temporarily diverges from the primary due to replication lag or transient network issues.
Internal Database Maintenance
Rare internal database processes or consistency checks might briefly alter an index's state, causing this error for concurrent operations attempting to use it.
Solutions
Coming SoonDetailed step-by-step solutions for this error are being prepared. In the meantime, try these general troubleshooting tips:
General Troubleshooting Tips
- Check the error message carefully for specific details
- Review recent changes that might have caused the error
- Search for the exact error code in the official documentation
- Check log files for additional context
- Try restarting the application or service