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ChangeFrequency
Change frequency is how often Google will be pinged with a new sitemaptells the search engine how often page content is updated. Change frequency is an estimate but sometimes page content can be changed due publishing of new information. Each time publish is completed, is potentially a reason to send the ping command to Google for a updating to the new version of the site map. But pinging Google too often may result in lower ranking, so it is advisable to select a less frequent scheme. Recommended is to ping Google monthly.sitemap.
Valid options for change frequency are always, hourly, daily, weekly, monthly, yearly, never
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