The question is too general. You may upgrade your application with service pack, reinstall the app from the scratches.
You haven't mentioned when your application is a client or server application.
You also haven't mentioned what is the nature of installation. Is your installation an upgrade, new version of software, bug fixes, or add on application. Is your software using push or pull installation? Do you have deployment server?
It is very much depends to the design of you application.
IBM Certified Database Administrator
Sun Certified Java Programmer
Oracle Certified Associate
Generally speaking, YES. You want to thoroughly test each load, like it was your first. Now this may be slightly different based on the complexity of the load, or if it was a patch or whatever. Still as a general rule of thumb, testing everything for any changes.
I figure if you have the courage to get out of bed in the morning, then how bad can the day be.