Typically, you start the AutoUpgrade JAR file in the Oracle home from which you are upgrading. However, the Oracle home must contain Java 8.

The AutoUpgrade utility is a Java 8 release JAR file, which is available in Oracle Database Oracle homes in releases after Oracle Database 12c Release 1 (12.1.0.2). On Oracle Database releases 12.2, 18 and 19, Java 8 is the default. The path to the Java version in the Oracle home is Oracle-home/jdk/bin/java, where Oracle-home is the Source database Oracle home (the earlier Oracle Database release that you are upgrading). For example:

$ORACLE_HOME/jdk/bin/java -version

The result should be a Java 8 version. For example:

$ORACLE_HOME/jdk/bin/java -version
java version "1.8.0_251"
Java(TM) SE Runtime Environment (build 1.8.0_251-b08)

A successful response to autoupgrade.jar -version should be similar to the following:

java -jar ./build/production/autoupgrade.jar -version
build.hash 2ce58db
build.version 19.7.4
build.date 2020/01/17 10:54:33
build.max_target_version 19
build.type production

If your you attempt to start AutoUpgrade with a Java release earlier than Java 8. then the following error occurs:

$ORACLE_HOME/jdk/bin/java -jar autoupgrade.jar -version
Exception in thread "main" java.lang.UnsupportedClassVersionError: Bad version number in .class file
    at java.lang.ClassLoader.defineClass1(Native Method)
    at ...