Misterious linkedid in CDR

[i]‘linkedid’ and ‘peeraccount’ are new CDR fields available to CDR aficionados.
linkedid is based on uniqueID, but spreads to other channels as transfers, dials,
etc are performed. Thus the pieces of CDR can be grouped into multilegged sets.

wiki.asterisk.org/wiki/display/ … win1.8-CDR[/i]

Cool! How to get that linkedid then? I 've added a VARCHAR field called ‘linkedid’ to my SQL table - but it’s empty.