Fallback to application-scoped resources occurs when an application avoids using the container-managed JNDI datasource and instead relies on resources bundled and loaded within the application itself. This can happen due to explicit configuration or as a backup mechanism when JNDI resources fail to initialise.

If the ojdbc.jar is missing from $CATALINA_HOME/lib, Tomcat cannot initialise the JNDI datasource, however, the application can still function if it directly loads the driver from WEB-INF/lib. Many legacy web applications were not designed to use container-managed JNDI datasources by default. They often have hardcoded connection logic as a fallback.