To record with Serato DJ and the XONE:DB2 and XONE:DB4 mixers you will need to set up the mixer for recording. You will need to designate a channel to use for recording and then select this channel in the REC panel in Serato DJ. This will record the software mix. You will not be able to use this channel for Serato DJ while it is used for recording.
Designating a channel is done from the XONE:DB2 and XONE:DB4 hardware using the Menu button and Display Screen. Navigate to ‘USB Routing’ and selecting ‘Record’ on the channel you want to use. You must then make sure Serato DJ is recording this nominated channel in the REC panel.
You can find out more about Routing and these menu features in the individual hardware User guide.