ERROR_IS_JOINED - 134 (0x86)
An attempt was made to use a JOIN or SUBST command on a drive that has already been joined.
Updated: Feb 21, 2026
Technical Meaning
The ERROR_IS_JOINED error code, represented by the numeric value 134 (0x86 in hexadecimal), indicates that an attempt was made to use a JOIN or SUBST command on a drive that has already been joined. This error is specific to operations involving virtual drives created using these commands.
Error Details
The JOIN and SUBST commands are used to create a virtual drive in the Windows file system, allowing directories to be mapped as drives or other directories to be joined with existing ones. Once a drive letter has been assigned through one of these commands, attempting to join it again will result in this error.
Common Causes
- Invalid Parameter Values: The command was issued with an already joined drive letter.
- Incorrect Object Type: The operation was attempted on an object that is not a directory or does not support joining.
- Exceeding Limits: The system may have limitations on the number of virtual drives that can be created, and attempting to exceed this limit will result in this error.
Real-World Context
This error typically occurs when a developer or user tries to reassign a drive letter to a directory that is already mapped. For example, if D: has been joined with another directory using the SUBST command and an attempt is made to join it again, this error will be returned.
Is This Error Critical?
The severity of this error depends on the context in which it occurs. While it does not indicate a critical system failure, it can disrupt intended operations if not handled properly.
How to Diagnose
To diagnose this issue, follow these steps:
- Review Operation Context: Ensure that the drive letter or directory being operated on is not already joined.
- Validate Parameters: Check the parameters passed to the
JOINorSUBSTcommand for correctness and completeness. - Confirm Object Types: Verify that the object being manipulated is a directory and supports joining operations.
How to Resolve
To resolve this issue, take these actions:
- Correct Parameter Usage: Ensure that the drive letter or directory is not already joined before attempting to join it again.
- Adjust Operation Context: If multiple virtual drives are needed, ensure they are created in a way that does not conflict with each other.
- Restore Data: In cases where data integrity might be compromised, restore any necessary files or directories.
Developer Notes
Developers should handle this error gracefully by providing appropriate feedback to the user and ensuring that operations do not proceed if a drive is already joined. This can prevent unexpected behavior in applications that rely on virtual drives.
Related Errors
- ERROR_SUBST_EXCEDENT: Occurs when the maximum number of substitions has been reached.
- ERROR_PATH_NOT_FOUND: May occur if the directory being joined does not exist.
FAQ
Q: What causes the ERROR_IS_JOINED error?
A: The error is caused by attempting to join a drive letter that is already in use or mapped as a virtual drive using JOIN or SUBST commands.
Q: How can I prevent this error from occurring?
A: Ensure that you do not attempt to join the same drive letter more than once. Validate your parameters and object types before executing the command.
Summary
The ERROR_IS_JOINED (0x86) error indicates an attempt to use a JOIN or SUBST command on a drive that is already joined. This error is specific to operations involving virtual drives created using these commands. Proper handling and validation of parameters can prevent this issue from occurring.