The Tomcat catalina.out file provides lots of details about what's going on with the Tomcat application server, the database connection, and extra application details like authentication/authorization.
It's an invaluable troubleshooting tool, and the Semarchy support team will often ask you to attach it to a support ticket.
Unix
Find the catalina.out log at /var/log/tomcat9/catalina.out
If your Semarchy xDM instance is on the cloud, you can use scp or a tool like Filezilla to download the log file to your computer to email it to the Semarchy support team.
Windows
Find the catalina.out log at <tomcat installation folder>\logs (example: C:\tomcat\logs)