Knowledge

ERROR_UNEXPECTED_MM_CREATE_ERR - 556 (0x22C)

If an MM error is returned which is not defined in the standard FsRtl filter, it is converted to one of the following errors which is guaranteed to be in the filter. In this case information is lost, however, the filter correctly handles the exception.

Updated: Feb 21, 2026

Technical Meaning

The ERROR_UNEXPECTED_MM_CREATE_ERR error code (556, 0x22C) is generated when an unexpected memory management creation error occurs. This error indicates that a specific memory management operation failed in a way that was not anticipated or defined within the standard FsRtl filter.

Error Details

When this error is encountered, it signifies that a memory management function has returned an error code that does not match any of the predefined errors in the FsRtl filter. As a result, the system converts this unexpected error into one of the predefined errors to ensure proper handling by the filter. However, this conversion process results in loss of specific information about the original error.

Usage Context

This error is typically encountered during operations that involve memory management within the Windows operating system. It can occur in various contexts such as file system operations, driver development, or any scenario where low-level memory allocation and deallocation are performed.

Developer Interpretation

Developers should interpret this error as an indication of a failure in a memory management operation. The specific nature of the error is not preserved due to the conversion process, making it challenging to pinpoint the exact cause without additional context or investigation. Developers should be aware that this error may indicate issues such as invalid parameters, incorrect object types, or exceeding system limits.

Related Errors

  • ERROR_INVALID_PARAMETER (0x57)
  • ERROR_OUTOFMEMORY (0x8C)
  • ERROR_NOT_ENOUGH_MEMORY (0x9F) These errors are related in that they all pertain to memory management issues, but they do not provide the same level of detail as ERROR_UNEXPECTED_MM_CREATE_ERR.

    FAQ

    Q: What does ERROR_UNEXPECTED_MM_CREATE_ERR mean?

    A: This error indicates an unexpected failure during a memory management operation. The specific cause is not preserved due to conversion into a predefined error code.

    Q: How can I troubleshoot this error?

    A: Review the context of the memory operation, validate parameters, and ensure that object types are correct. Consider checking for any system limits or constraints that might be in place.

    Summary

    The ERROR_UNEXPECTED_MM_CREATE_ERR error is a generic indication of an unexpected failure during memory management operations within Windows. While it provides some level of information about the nature of the issue, developers should take additional steps to diagnose and resolve the underlying problem.