Magento – Some cron jobs are just skipped

Records in the cron_schedule table which are stuck in the running status like this are generally due to the PHP process encountering a fatal error. When a fatal error occurs, the job is halted, and Magento does not attempt to cleanup records left in the running status regardless of how long ago the execution was attempted.

In the example above, you are showing a record which has been hanging around for a few months. Those can be manually removed without causing any harm. A word of warning though… be careful not to remove running records which are for the current day (or previous day to be safe) as doing so will cause errors when the cron job is cleanup up after finishing the job.

If the same job is consistently failing and leaving these around, i.e. not going to a completed status very often, you'll want to dig into your PHP error logs and find out what the problem is. Considering you have over a hundred of these, I would take a look at your error logs to find the root cause. It may even be as simple as needing to increase the memory allocated to the PHP process running the cron, but could also be the result of a bug in the code which would need to be patched.

First of all, make sure the cron is set on your server. Try the following command using SSH

#crontab -l

There should be your magento_root/cron.php file.

If not, then you need to edit the crontab. Use the following commands

#crontab -e       
(this will open crontab in your default editor)

*/5 * * * * wget -O  /dev/null -q path_to_magento_root/cron.php > /dev/null
(add this statement and save and close the file. 
This will check your magento cron.php after every five minutes)

Now, magento cron is set on your server.

I'd also recommend you this extension AOE_SCHEDULLER. This will help you monitoring all magento crons.