If you are currently running an M2 version (zcs-3.0.0_M2_740 or 746) and want to upgrade to 3.1.1, you must perform the workaround in the following thread:

If you don't perform the workaround before attempting the upgrade, then the installation will abort half-way and you will have to revert to your M2 backup.

According to Bugzilla, this bug is targetted for Edison (3.2):