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I have a major problem with my system's cron; it runs every 3 minustes causing a slow responding from the site. When I checked the logs, I found this error:
Attempting to re-run cron while it is already running.
I found some good answers on Cron stopped running; logs say: "Attempting to re-run cron while it is already running." but when I searched for the cron_semaphore variable in variable's table I didn't find it.
Even after I disabled the Search module, and uninstalled it, nothing happened: The cron tasks are still not working.
I checked, and I noticed that the cron tasks have been executed 1 day and 7 hours ago, although I configured it to run every 12 hours.
I am using Drupal 7.19.