Getting errors while starting the windchill server- Prod down

In order to remove unreferenced files from the vault wanted to set the wt.fv.purgeUnreferencedFilesOlderThan =2

I just did the following steps as initial step for removing the .unreferenced files:

1) Updated site.xconf to set wt.fv.purgeUnreferencedFilesOlderThan =2

2) Ran xconfmanager –p from Windchill home directory

3) No error reported

4) Stopped Windchill

5) Cleared tomcat instances

6) After that tried to start the method server but it’s not starting

Getting following error

Exception in thread "main" java.lang.reflect.InvocationTargetException

        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:597)

        at wt.manager.ServerLauncher.startServerReturningProcess(ServerLauncher.java:143)

        at wt.manager.ServerLauncher.startServer(ServerLauncher.java:101)

        at wt.manager.ServerLauncher.main(ServerLauncher.java:472)

Caused by: java.lang.IllegalArgumentException: Empty command

        at java.lang.Runtime.exec(Runtime.java:425)

        at java.lang.Runtime.exec(Runtime.java:369)

        at wt.manager.ServerLauncher.launchCmd(ServerLauncher.java:236)

        at wt.manager.ServerLauncher.launchCmd(ServerLauncher.java:208)

        at wt.manager.ServerLauncher.launchCmd(ServerLauncher.java:192)

        at wt.manager.BaseServerLauncher.launch(BaseServerLauncher.java:249)

        at wt.manager.BaseServerLauncher.launch(BaseServerLauncher.java:122)

        ... 7 more

Any idea why this error is showing up? Please let me know currently our prod servers are not starting.