The following issue appears when running a post install step in 17.3 GA installation:
Exception occurred while running postInstallAction
Action [content=pdm_webcache -H, dir=, relPath= ....
Release: 17.3 or higher
Component: CA Service Desk Manager
Database connection details are incorrect. SDM was not able to start due to a connectivity issue with the DB.
It's recommended to start the upgrade from scratch (restore snapshots) and enter the right information in the database connection details step of the installation/upgrade. Engage the DBA if necessary to provide the right information (port, instance name, hostname, etc)