Failed to migrate Panorama from Legacy mode to Management-Only mode.

• Trying to switch panorama from legacy mode to management-only mode.
• Error "cannot switch to management-only mode; all devices must be included in log-collector-group(s)" is seen.

admin@Panorama> request system system-mode management-only
Executing this command will change the system to management-only mode, logs will be removed. This will restart the system. Are you sure you want to continue? (y or n)

Server error : Failed to change to management-only mode.
cannot switch to management-only mode; all devices must be included in log-collector-group(s).

• PANOS: 11.0
• Panorama

• The Panorama is not connected to any log collector.
• By default, we don't have an additional 2TB logging disk to configure the log collector in legacy mode.
• The Panorama virtual appliance in Legacy mode uses approximately 11GB on its internal disk partition for log storage. Refer to the Admin Guide

1. Create a dummy Log Collector under GUI: Panorama > Managed Collectors with a dummy serial no. eg. 123456789

2. From WebUI navigate to Panorama > Collector Groups, and configure a dummy Log Collector Group named 'Test-CG'.
3. Commit and Push (But this Push has to be done only to the collector group).
4. From the CLI, run the command "request log-migration-set-start". This allowed adding a collector without disks to the collector group.
5. From the CLI, run the below commands:

> configure
# set log-collector-group Test-CG logfwd-setting collectors <collector-name>
# commit force
# exit

6. From the WebUI, Again navigate to Panorama > Collector Groups > Test-CG > Device Log Forwarding > Add, then Modify the 'Devices' section to include all the managed devices.
7. Commit the changes locally on the Panorama.
8. Afterwards, Change the Panorama system mode to management-only using the CLI command "request system system-mode management-only"
9. Once the Panorama boots up in management-only mode, delete the dummy Log Collector Group and  Log Collector.