What is in /opt/local/var/db/dports

[Markus Weimer]

Hi,

I just checked my system for places where I can get a few megabytes of
diskspace back and found that /opt/local/var/db/dports contains quite
a lot of files. Essentially all software packages I installed are
there once again. Is it safe to delete them? Is there a general
procedure to free as much space as possible while keeping the ports
intact?

Thanks in advance for any pointers,

Markus