Background & Resume Tab (Preferences Dialog)
The Transfer on background by default checkbox makes WinSCP to perform all transfers on background. You can always alter this for particular transfer on transfer options dialog (if enabled).
You can check No confirmations for background transfers to avoid overwrite and other confirmations for the background transfer.
Use Remember password of main session for background transfers checkbox to avoid background transfers asking for password. WinSCP will save the main session password and reuse it for background transfer connections. Note that for this WinSCP must keep the password in memory, what may have security implications. If you have the password saved in stored session, what is not recommended at all, the saved password is used automatically for background transfers.
Transfer Resume/Transfer to Temporary Filename
WinSCP is able to store file being transferred to temporary filename first, renaming it to the target name only once the transfer successfully finishes.
Reasons to do that:
- If the transfer is interrupted, on the next attempt, WinSCP is able to detect the partial/temporary file and suggest you transfer resuming automatically (or even resume automatically).
- While updating an existing file, the original version of the file exists during whole transfer. This is particularly useful when updating frequently accessed file on web sites.
Reasons not to do that:
- As the file is uploaded to a temporary name, it is technically a new file, even though the file with target name already exists. So after the original file is deleted and temporary file is renamed to the original file name, you loose all attributes of the original file (such as owner and group) except for permissions.
For performance reasons transfer to temporary file name is enabled by default for files larger then a given threshold. The threshold is initially 100 KiB. You can change the threshold. You can also enable the feature for all files, particularly when looking to achieve the second impact. You may also need to disable the feature altogether, particularly if you do not have permissions required (e.g. permissions to create a new file in target directory).