The -disableSizeCommand option is used to define whether the server supports the SIZE command. The SIZE command is described in the manual “interNet Services User Guide”.
A problem in conjunction with the SIZE command is that the SIZE command generally needs to read the file to be investigated fully before it can send a correct message about the file size. Execution of the size command is thus resource-intensive and time-consuming, especially with large files.
The result of this is
a weakness with regards to “Denial of Service” attacks,
problems with some FTP clients.
At the start of transfer these clients execute the SIZE command so as to display a progress bar indicating the relative progress of the transfer. Disregarding the question as to whether this progress bar justifies the relevant file being read twice by the server, the problem is encountered on at least one of the clients that it clears the connection after a fixed period, which cannot be modified by the user, without a message being issued by the server. This client is thus not suitable for transferring very large files. You must bear in mind that the client issues the SIZE command even if the progress bar is disabled.
If you need to support clients of this type, is makes sense to disable the SIZE command with the -disableSizeCommand option. You must bear in mind here that it may then not be possible to execute the client commands reget and reput on the server involved.
-disableSizeCommand |
NO | YES |
NO
Support of the SIZE command is not disabled.
NO is the default.
YES
Support of the SIZE command is disabled.