Qlik provides a tool called Repository Snapshot Manager (RSM) to do it for you.
Please note that it's not working very well with Shared Persistence (QS 3.2), but works perfectly with Sync Persistence so far.
Here is the info:
You just need to create a BAT file and schedule it's execution via Windows Scheduler on the server.
Please note that RSM stops Qlik Services while running, so your system might be down for few minutes...
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