These allow you to see individual files when you do a restore.
If you compress your catalog it will compress them and add the .Z suffix.
Please do not manually uncompress or compress them, since you can potentially confuse your catalog (which is a bad thing) and you can find yourself being unable to restore from that image.
You are pretty much limited to setting the compression, and then running
/usr/openv/netbackup/bin/admincmd/bpimage -cleanup -allclients
nbdelete -allvolumes -force
bpexpdate -deassignempty -force
IF your compression / uncompression gets jacked up, you MAY be able to uncompress everything, then recompress it, to get it back to a steady state.
The compress used for 'compressing' the catalog .f files was changed (fairly recently, 7.7 if I recall correctly). Simple, instead of the .f files becoming .f.Z which was when the unix 'compress' command was used, NBU know does it's own compression and the the file suffix becomes .Z1
Catalog compression compresses the ,f files (as these are the 'big part' of the catalog), hence when you see the the .f.Z1 files, these are simply the .f files once they have been compressed.