After trying to open /index.php?module=MultiSites&action=index&idSite=1&period=range&date=2016-10-01,2016-12-31
which is a 3 months long report, I got this error:
Oops… there was a problem during the request. Maybe the server had a temporary issue, or maybe you requested a report with too much data. Please try again. If this error occurs repeatedly please contact your Piwik administrator for assistance.
What can I tune to run such long reports?