Knowledge Base

Problem

Users find an unexpected .vtl file in their EthoVision experiment folder and are unsure what it is, whether it is safe to delete, or whether it indicates a problem.

Details

.vtl files are not documented in the EthoVision help documentation, causing confusion — particularly when experiment folders are moved to a network location and the file becomes visible to multiple users. The file may persist in the folder even when the experiment is not currently open.

Solution

1. A .vtl file is a **lock file** automatically created by EthoVision when an experiment is opened. Its purpose is to provide exclusive access to the experiment and prevent simultaneous editing by multiple users.
2. Under normal operation, EthoVision deletes the .vtl file automatically when the experiment is closed.
3. If EthoVision **crashes** while the experiment is open, the .vtl file is not deleted and will remain in the folder. It will be removed automatically the next time the experiment is successfully opened and closed.
4. **It is safe to delete a .vtl file manually** if you are certain the experiment is not currently open on any computer (e.g., after a crash). Verify no other user has the experiment open before deleting.
5. The presence of a .vtl file when the experiment is not open indicates a prior crash or improper shutdown — no data corruption is implied by the file itself.
6. If working on a network drive, ensure only one user opens the experiment at a time; the .vtl file is the mechanism that enforces this.