We are doing a pega update from 7.1.8 to 7.2.0, when we run the update script from our db server we are getting the following error. we are trying to run from our db server with the  help of dba and we found out we are in version 7.1.5. Wanted to know what java version we should be in .

BUILD FAILED
/DBA01/EXPBACK/USRSM4D/scripts/setupDatabase.xml:55: java.lang.UnsupportedClassVersionError: Bad version number in .class file
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
        at org.apache.tools.ant.AntClassLoader.defineClassFromData(AntClassLoader.java:1136)
        at org.apache.tools.ant.AntClassLoader.getClassFromStream(AntClassLoader.java:1307)
        at org.apache.tools.ant.AntClassLoader.findClassInComponents(AntClassLoader.java:1362)
        at org.apache.tools.ant.AntClassLoader.findClass(AntClassLoader.java:1323)
        at org.apache.tools.ant.AntClassLoader.loadClass(AntClassLoader.java:1076)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:242)
        at org.apache.tools.ant.taskdefs.Definer.addDefinition(Definer.java:579)
        at org.apache.tools.ant.taskdefs.Definer.loadProperties(Definer.java:408)
        at org.apache.tools.ant.taskdefs.Definer.execute(Definer.java:264)
        at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:292)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:592)
        at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
        at org.apache.tools.ant.Task.perform(Task.java:348)
        at org.apache.tools.ant.Target.execute(Target.java:435)
        at org.apache.tools.ant.helper.ProjectHelper2.parse(ProjectHelper2.java:180)
        at org.apache.tools.ant.ProjectHelper.configureProject(ProjectHelper.java:93)
        at org.apache.tools.ant.Main.runBuild(Main.java:826)
        at org.apache.tools.ant.Main.startAnt(Main.java:235)
        at org.apache.tools.ant.launch.Launcher.run(Launcher.java:280)
        at org.apache.tools.ant.launch.Launcher.main(Launcher.java:109)
 

**Updated by Moderator: Vidyaranjan. Removed user added Ask the Expert tags. Apologies for confusion, shouldn't have been an end-user option***