DB Upgrade Tool 2.0.1 is bundled with the DXP 7.1 SP1 bundle, but the default paths that are suggested don't match up with the environment variables that are present in the bundle itself.
For example, the DXP 7.1 SP1 bundle comes with Tomcat 9.0.6 and the Tomcat home is ../liferay-dxp-18.104.22.168-sp1/tomcat-9.0.6, but the DB Upgrade Tool suggests ../liferay-dxp-22.214.171.124-sp1/tomcat-9.0.10 by default. If a user goes through this process without checking the path, it results with a Exception in thread "main" java.lang.ClassNotFoundException: com.liferay.portal.tools.DBUpgrader which is a bit confusing.
Steps to Reproduce
1. Obtain liferay-dxp-tomcat-126.96.36.199-sp1-20190110085705206.zip
2. Extract the ZIP file
3. Go to ../liferay-dxp-188.8.131.52-sp1/tools/portal-tools-db-upgrade-client
4. Run java -jar com.liferay.portal.tools.db.upgrade.client.jar or db_upgrade.sh (db_upgrade.bat on Windows)
5. Go through the wizard, and hit Enter when you see the prompt for
Please enter your application server (tomcat):
6. Notice the next line that appears
The default path does not correspond to the actual version of Tomcat that is in the bundle:
Please enter your application server directory (/Users/Liferay/bundles/liferay-dxp-184.108.40.206-sp1/tomcat-9.0.10):
The default path corresponds to the actual version of Tomcat that is in the bundle:
Please enter your application server directory (/Users/Liferay/bundles/liferay-dxp-220.127.116.11-sp1/tomcat-9.0.6):