FTP Connection Failing to IBM i AS/400


I am testing the software to see if it will meet our needs. I have attempted to configure the FTP Server Settings for an FTP server that is running on the IBM i Operating System, V7R4 (aka AS/400). I can successfully connect with either Plain FTP or FTPS (implicit) using WinSCP and FileZilla. I have appropriate permissions, as I can upload files successfully with other FTP clients. However, I keep receiving the following error:

“The requested operation is not supported”.

I have turned on the “Trace” logging in the Advanced Log options. Please see attached picture for sample plain FTP configuration. If you would like to see the Trace log, please instruct me how to securely send it to you.

Thank you,

Hi Jacob_Banda,

To investigate this case we need more details. Could you please send us your Advanced log? Here are more details on how to do it https://sqlbackupandftp.com/blog/how-to-send-log-to-developers

Please let us know when the log will be sent and your Application ID (‘Help’ > ‘About’).

Sorry for the inconvenience.

Hello Alexander,

I have uploaded the logs and responded with the Application ID via email.

Hi Jacob_Banda,

We have checked your logs and found out that your server doesn’t support the SIZE command.

When sending the command:
SIZE /windata/sqlserver/SqlBakTest-1853926821.bak

The server returns the following message:
500 Subcommand SIZE not valid.

For the correct work of the application, it is needed to either provide support for the command by your FTP Server, or you can disable the option to verify files after downloading (but this is not very secure, as a broken backup can be uploaded to the destination).

Sorry for the inconvenience.

Thank you for taking the time to identify the problem!

I hope this post helps other members who might be trying to use an FTP server running on an IBM i Power System (AS/400). As a side note, I have reached out to IBM to see if they have any suggestions on how to achieve the same results from the SIZE command with other supported subcommands. Perhaps you could take a look at it down the road. I’ll share with you what they tell me.

Sure, thank you.

Please feel free to contact us on any issues or concerns.