I have a Tomcat instance running an openrdf-sesame environment. By default the location of my openrdf-sesame database configuration and data is at %APPDATA%\aduna. I am trying to change where this data saves to something custom like C:\aduna. I have looked at documentation online, but it does not specify if this is defined in a configuration file somewhere or if it is an hard coded location. I also saw that RDF4J is a new replacement for openrdf-sesame? I wouldn't mind upgrading if I could achieve the result of specifying where to save my data. Any ideas?
OpenRDF Sesame is no longer maintained, it has been succeeded by the Eclipse RDF4J project. There is a migration guide available to help you figure out what to do when updating your project.
Although the Sesame project is no longer maintained, a documentation archive is available, and of course a lot of the RDF4J documentation also applies to Sesame, albeit with slightly different package names.
As for your specific question: the directory Sesame Server uses is determined by the system property info.aduna.platform.appdata.basedir. Set this property (at JVM startup, using the -D flag) to the desired location. See the archived documentation about application directory configuration for more details. As an aside: note that in RDF4J this property has been renamed (to org.eclipse.rdf4j.appdata.basedir), so if you upgrade to RDF4J, be sure to change this.