Planning Book Data outside planning horizon

Hi Experts,

I am new to APO  "Data partly after horizon 01.04.2010 to 01.04.2016"  message is coming when accessing planning book  in our production system, not in Testing/Quality system .refer attachment

when I gone through the forum we have to extend planning area using program  /SAPAPO/TS_PAREA_INITIALISE.

To perform this activity  is  back up of the cube compulsory we have to do?

Please let me know is any other steps to follow to resolve this issue, with this issue the users are not able to access planning book.

Thanks & Regards,

Srihari.M