You can enable debugging by:
1. Use -debug option with commands.
Ex: #/opt/omni/bin/omnib -oracle8_list 2TBbackup -debug 1-300,C:1024000 2TBbackupDebug.txt
2. Else from Windows GUI, click files on top left -> Preferences -> debugging ; Give filename and select option to start debugging. Restart GUI.
By default, Debugs will be created on /tmp in linux and programdata\omniback\tmp.
Log Level can be 1-100, 1-200, 1-300, 1-500. Last one will generate more number of logs and logs each info. So make sure space usage.