I am trying to upgrade from Version 9.4 build 9400 using the following file i.e  "ManageEngine_ServiceDesk_Plus_9_4_0_SP-1_0_0.ppm"

But its showing uninstallation completed with the below error in dos prompt in the background.

Could not create connection; - nested throwable: (org.jboss.resource.JBossResourceException: Failed to register driver for: org.postgresql.Driver; - nested throwable: (java.lang.ClassNotFoundException: org.postgresql.Driver)); - nested throwable: (org.jboss.resource.JBossResourceException: Could not create connection; - nested throwable: (org.jboss.resource.JBossResourceException: Failed to register driver for: org.postgresql.Driver; - nested throwable: (java.lang.ClassNotFoundException: org.postgresql.Driver)))
Database server not running.

 Kindly help in patch up-gradation.