Summary and Info:
Previously, when a local copy of the pacman sync database was not available it was still possible to perform offline actions (eg pacman -U somefile.pkg.tar.xz), however this is no longer possible. Instead you now receive several errors referring to the unfindable database files, and then pacman completes with an error: "error: failed to prepare transaction (could not find database)"
I believe this has occurred since the version 4 release.

On my netbook, /var/lib/pacman/sync/ is mounted as a ramfs, hence why I find this to be a problem - for example when rebuilding the catalyst module package and reinstalling while offline.

Steps to Reproduce:
rm -rf /var/lib/pacman/sync/*
pacman -U somefile.pkg.tar.xz