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ERROR_IS_JOINED
What ERROR_IS_JOINED means
ERROR_IS_JOINED is a Win32 system result whose documented message is: “An attempt was made to use a JOIN or SUBST command on a drive that has already been joined.” In practical troubleshooting, it belongs to legacy drive mapping in which the requested drive is already joined into another directory location.
Typical causes
- the same JOIN command runs twice
- cleanup failed during a previous session
- multiple tools assume ownership of the mapping state
How to investigate the result
- list active mappings and compare source and destination paths
- Identify whether the existing JOIN is equivalent or conflicting
- Verify commands execute under the same user/session namespace
Developer guidance
Query state before mutation and record ownership of mappings created by the application. Remove only mappings the application can prove it owns.
Administrator and support guidance
Eliminate duplicate logon scripts and document the intended drive topology. Prefer modern volume mount points for maintained systems.
Example
A legacy application setup reruns after a partial install and attempts to JOIN the same drive again, producing this result.
How it differs from related results
It describes the source drive already being joined; ERROR_IS_JOIN_TARGET describes a drive containing a directory that serves as the target.
References
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