The DB.UpdateDevice.Text field acivity allows you to update any of the text fields in the CatTools database Device table.
It does not run against your physical network devices as all the other Activities do but is instead used to do batch processing against multiple devices within the CatTools database Device table.
An example use of this Activity might be:
Your network devices use a RADIUS or TACACS server for remote authentication. You have just changed the username on the RADIUS/TACACS server and you now need to update all of your devices within CatTools with this new information.
Instead of editing each device individually you would create a new DB.UpdateDevice.Text field activity which will apply the new username to all of your Devices at once.
For more information see Setting up the activity