Knowledge

ERROR_DS_EXISTS_IN_POSS_SUP - 8395 (0x20CB)

Schema deletion failed: class is used as poss superior.

Updated: Feb 21, 2026

Introduction

This article provides a detailed technical explanation of the ERROR_DS_EXISTS_IN_POSS_SUP error code, which is encountered during schema deletion operations in Windows Active Directory. The error indicates that an attempt to delete a class from the directory schema failed because this class is currently used as a possible superior (POSS_SUP) for another class.

Technical Background

The Windows Active Directory schema defines the structure and properties of objects within the directory. Each class in the schema has attributes, including POSS_SUP, which specifies the classes that can be its superiors. During operations such as schema modification or deletion, the system checks these relationships to ensure data consistency.

Error Details

  • Error Name: ERROR_DS_EXISTS_IN_POSS_SUP
  • Numeric Code: 8395 (0x20CB)
  • Short Description: Schema deletion failed: class is used as poss superior.

This error occurs when an attempt to delete a schema class that has been designated as a possible superior for another class fails. The system cannot remove the class because it would violate the integrity of the directory structure.

Common Causes

  • Invalid Parameter Values: An incorrect or invalid class identifier was provided during the deletion operation.
  • Incorrect Object Type: The operation attempted to delete an object that is not a schema class, but rather a different type of object such as a user or group.
  • Exceeding Limits: The system may have encountered limitations in handling schema modifications, though this error specifically indicates a logical constraint rather than a resource limit.

Real-World Context

This error typically arises during administrative tasks that involve modifying the Active Directory schema. For example, an administrator might attempt to delete a class that is still referenced by another class as a possible superior, leading to this error message.

Is This Error Critical?

Yes, this error indicates a critical issue with the directory structure and should be addressed promptly to maintain data integrity.

How to Diagnose

  1. Review Operation Context: Ensure that the operation is being performed on a schema class and not another type of object.
  2. Validate Parameters: Verify that the correct class identifier is used in the deletion command or script.
  3. Confirm Object Types: Use tools like dsmod to check the attributes of the classes involved, particularly their POSS_SUP values.
  4. Verify Input Data: Ensure that no other objects depend on the class being deleted as a possible superior.

How to Resolve

  1. Correct Parameter Usage: Double-check and correct any parameter values if they are incorrect.
  2. Adjust Operation Context: If the operation context is incorrect, adjust it to ensure it targets the appropriate schema class.
  3. Restore Data: If necessary, restore data from a backup or use tools like dsmod to modify the schema relationships.
  4. Retry Operation with Valid Inputs: Once the issue is identified and corrected, retry the operation with valid inputs.

Developer Notes

When working with Active Directory schema modifications, always ensure that you understand the dependencies between classes. Use appropriate tools and scripts to validate and manage these relationships before making changes.

Related Errors

  • ERROR_DS_OBJECT_NOT_FOUND (1932)
  • ERROR_DS_CANT_MOD_OBJ (5460)
  • ERROR_DS_SCHEMA_MUST_BE_NATIVE (8397)

FAQ

Q: What does the error code 8395 mean?

A: The error code 8395 indicates that a schema class cannot be deleted because it is used as a possible superior for another class.

Q: How can I avoid this error?

A: Ensure that you understand the dependencies between classes in the Active Directory schema before making any modifications. Use tools like dsmod to check and manage these relationships.

Summary

The ERROR_DS_EXISTS_IN_POSS_SUP (8395) error occurs when an attempt to delete a schema class fails because it is used as a possible superior for another class. This error highlights the importance of understanding Active Directory schema dependencies and ensuring that modifications are made with appropriate caution.