Prerequisite check "CheckSystemSpace" failed.So with a bit of hacking I got around it by displacing the ./patch_storage directory and forcing opatch to stop doing a file system check (basically no "df -h" )
The details are:
Required amount of space(17499.766MB) is not available.
1.) displace ./patch_storage to a mount with enough space (but keep a backup in place just in case...)
cp -r /FMWH/Oracle_BI1/.patch_storage /data/NASmnt00001/
2.) create a symbolic link to take the place of ./patch_storage
ln -s /data/NASmnt00001/.patch_storage ./.patch_storageAfter this step if you execute opatch normally, it will still fail with "CheckSystemSpace" failed.
3.) Have opatch omit the space check:
opatch napply -silent /data/NASmnt00001/18.104.22.168.140114 -id 16569379,16913445,16997936,17300045,17300417,17922352,17922552,17922577,17922596 OPatch.SKIP_VERIFY_SPACE=true
(h/t @G_Ceresa for being picky and getting on my nerves with "That's not proper." ... I said it's a hack, mate ;-))