Debugging File Transfer

Tectia Server for IBM z/OS uses a separate proces, sft-server-g3 for file transfer operations.

To obtain debug information from sft-server-g3, you can use the environment variables SSH_SFTP_DEBUG, SSH_SFTP_DEBUG_FILE, and SSH_DEBUG_FMT.

When the debugging is enabled, the sft-server-g3 debug messages are by default sent to the standard error, that goes also to the SFTP client. If you want to forward the sft-server-g3 debug messages into a file and not to the client, you can add the following two environment variables affecting the secure file transfer user into the /etc/environment file or the user-specific $HOME/.ssh2/environment file on the server:

SSH_SFTP_DEBUG defines the debug level that controls the messages that the sft-server-g3 process will be showing while executing. To get some debug data, you can use, for example:
```
SSH_SFTP_DEBUG="Sftp"=12"
```
To get more details, you can use, for example:
```
SSH_SFTP_DEBUG="Sftp*=12,SshFile*=12"
```
To get even deeper level of detail, you can use, for example:
```
SSH_SFTP_DEBUG="Sftp*=15,Ssh*File*=15,Ssh*Dir*=15"
```
To get full debugging information from the SFTP server, use:
```
SSH_SFTP_DEBUG="Sftp*=20,Ssh*File*=20,Ssh*Dir*=20"
```
To get most low-level z/OS debugging information:
```
SSH_SFTP_DEBUG="*Mvs*=17"
```
To get all low-level z/OS debugging information:
```
SSH_SFTP_DEBUG="*Mvs*=99"
```
To get all debugging information related to dataset allocation:
```
SSH_SFTP_DEBUG="SshFileMvsAllocate=99"
```
To get all debugging information related to z/OS catalog:
```
SSH_SFTP_DEBUG="SshFileMvsCatalog=99"
```
SSH_SFTP_DEBUG_FILE defines the file where the debug messages from the sft-server-g3 will be printed. The value can be for example:
```
SSH_SFTP_DEBUG_FILE=/tmp/sft_debug.txt
```
Note that the path must be given without citations marks. If this variable is not defined, the messages will be sent to standard error and the SFTP client will receive them.
SSH_DEBUG_FMT defines the format of the debug messages. The default variable used is:
```
SSH_DEBUG_FMT="%Dd/%Dt/%Dy %Dh:%Dm:%Ds:%Df %m/%s:%n:%f %M"
```
For more information on the syntax of this variable, see the sftpg3.1 man page.

On the client side, it is also possible to use the debug command of sftpg3 to get debugging information. For example, to get basic debugging data, give the command:

sftp> debug "Sftp*=2"

The same debug strings as with SSH_SFTP_DEBUG can also be used.