Knowledge

ERROR_DS_NAME_TYPE_UNKNOWN - 8351 (0x209F)

The directory service cannot get the attribute type for a name.

Updated: Feb 21, 2026

Technical Background

The ERROR_DS_NAME_TYPE_UNKNOWN (8351, 0x209F) is a specific error code encountered in the context of directory services within the Windows operating system. This error indicates that the directory service was unable to determine the attribute type for a given name during an operation.

Error Details

The ERROR_DS_NAME_TYPE_UNKNOWN error typically arises when the directory service attempts to resolve or manipulate a name but fails to identify its associated attribute type. This can occur in various operations, such as adding, modifying, or querying entries within Active Directory.

Common Causes

  • Invalid Parameter Values: The operation was performed with an invalid parameter that did not correspond to any known attribute type.
  • Incorrect Object Type: The name provided does not match the expected object type for the operation being performed.
  • Exceeding Limits: The directory service may have encountered a limit on the number of operations or names it can process simultaneously.

Real-World Context

This error is often observed in scenarios where complex queries or modifications are attempted against Active Directory. For example, if an attempt is made to modify a user attribute without specifying the correct attribute type, this error may be returned.

Is This Error Critical?

The criticality of this error depends on the context and the specific operation being performed. In most cases, it indicates that the operation cannot proceed as intended due to missing or incorrect information.

How to Diagnose

  1. Review Operation Context: Verify the context in which the operation was initiated.
  2. Validate Parameters: Ensure all parameters are correctly specified and match the expected attribute types.
  3. Confirm Object Types: Confirm that the names provided correspond to the correct object types for the intended operations.

How to Resolve

  1. Correct Parameter Usage: Ensure that all parameters used in the operation are valid and correctly typed.
  2. Adjust Operation Context: If necessary, adjust the context or scope of the operation to ensure it aligns with the expected attribute types.
  3. Restore Data: In cases where data corruption is suspected, restore from a known good backup if available.

Developer Notes

Developers should be cautious when performing operations that involve complex names and attributes in Active Directory. Ensuring that all parameters are correctly typed can prevent this error from occurring.

Related Errors

  • ERROR_DS_ATT_NOT_DEF_IN_SCHEMA (8357): The attribute is not defined in the schema.
  • ERROR_DS_NAME_NOT_FOUND (1902): The name specified does not exist in the directory service.

FAQ

Q: What causes this error?

A: This error typically occurs when an operation is performed with invalid or incorrect parameters, leading to a failure in determining the attribute type for a given name.

Q: How can I prevent this error?

A: Ensure that all parameters used in operations are correctly typed and match the expected attribute types. Validate input data before performing complex directory service operations.

Summary

The ERROR_DS_NAME_TYPE_UNKNOWN (8351, 0x209F) is a specific error code indicating an issue with name resolution or attribute type determination in Active Directory. Understanding its context and causes can help in diagnosing and resolving issues more effectively.