You may want to review this blog post from David Musgrave: blogs.msdn.com/.../how-to-identify-the-security-tasks-and-security-roles-associated-with-a-specific-window-or-report.aspx
According to David the Security Resource Descriptions table (SY09400 in SQL) was added in GP 10.0, when the security model changed, and is initially empty but can be populated by running the Clear Data File Maintenance process on it. The system will then rebuild the contents based on the current installed dictionaries.
So...while this process may remove the data currently in the Security Resource Descriptions table if it is not empty, it will rebuild the contents based on your current GP install. I have run this process many times for many different customers to allow for reporting on the security setup in GP 10.0 and 2010 and have not seen any problems afterwards.