can i use the file on target

That is correct. Since the file is open on the Target, you will see a Blocked File in RepliStor because it can not write the the actual file on the destination disk.

You do have this option that can override this:
Maintenance -> Options -> Advanced -> Set Expiration Time for Open Files on Target

When this is set, it will tell RepliStor to close the target file so it can be updated.

I am not sure the reason you would need to open files ont he Target, unless you are doing testing or something. But to ensure data consistency issue do not arrise, you can always:
- Disable the Spec
- Make files changes on the Target.
- Close the file.
- Enable the Spec
- Sync the Spec

NOTE: Any changes made to the Target file will be lost.

If you have Target File Protest enabled, then the Files on the Target node will be locked by RepliStor. You can view these files, with a read only program like Notepad.exe, but you cannot open them with the intention of making changes.

If you do not turn on Target File Protection. then RepliStor allows you to write to the files on either the Source or the Target node. However, if you make changes to the file on the Target, these changes are not generally updated on the Source node. Therefore you run the risk of losing these changes. This is a very dangerous choice and that means that you are responsible for making sure that the files are only updated on one machine and RepliStor is not aware of the updates. If you do a sync in this case, the changed files on the Target will be overwritten by the file from the Source nd the changes will be lost.

That is why the default behavior is to protect the Target's files by locking them. Make sure you fully understand the way this works by testing with non-production data before trying it with real data files. Even then, you should have a complete backup before trying any circular replication of unprotected target files.