Manually Clean Dispatcher Cache

We have a requirement that we update some details of a page from a feed after certain interval of time and then we need to clean the dispatcher cache.

We have done few sling mapping also

e.g.

for page  /content/mysite/page1.html we have defined a sling mapping and whenever a request comes for http://domainname/mysite/page1.html it serves /content/mysite/page1.html

Cache generated : /mysite/page1.html in docroot folder

Once the page data is updated by the feed, we need to clean the cache.

I am trying to manually clean the cache by making following  POST request at http://domainname/dispatcher/invalidate.cache with parameters

CQ-Action: Activate
CQ-Handle: /mysite

Content-Length: 0

It returns 201 with following but the cache is not deleted.  Am I doing something wrong ?

Any help will be much appreciated.

Regards,

-Yogesh