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). 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@sales]$ $ORACLE_HOME/jdk/bin/java -version
java version "1.8.0_152"
Java(TM) SE Runtime Environment (build 1.8.0_152-b16)
Java HotSpot(TM) 64-Bit Server VM (build 25.152-b16, mixed mode)

When you upgrade Oracle Database 11g Release 2 (11.2.0.4) or earlier releases, you can use AutoUpgrade. However, because Java 8 is not available in the Oracle Database Oracle homes for Oracle Database 11g Release 2 and earlier releases, you must start AutoUpgrade from the Java release in the Target Oracle home (the Oracle home to which you are upgrading), or install Java 8 in your Source Oracle home.

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

[oracle@sales ~]$ $ORACLE_HOME/jdk/bin/java -jar autoupgrade.jar -version
build.version 20190201
build.date 2019/02/01 11:50:22
build.label RDBMS_PT.AUTOUPGRADE_LINUX.X64_190131.1800

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 ...