You should be running Oracle Empirica Signal release 9.1 or later before upgrading to release 9.2.3.

You can upgrade from releases 9.1.0.x, 9.2.0.x, 9.2.1.x, or 9.2.2.x. to release 9.2.3.

If upgrading from versions before 9.0, please use the 9.0 upgrade guide as first step.