Upgrading from v7.6.x to v7.8.x/content/support/library/data/v78/upgrade/dss_upgrade_76_to_78.pdf
Before you upgrade to v7.8.x, you must first upgrade it to v7.7.2. You cannot upgrade directly to v7.8.x.
The required upgrade path is as follows:
7.6.x > 7.7.2 > 7.8.x
Click View Complete Document for more.