The limit_time_real_cron setting is used to limit the maximum execution time for a cron job in real time. This setting can be useful in preventing long-running cron jobs from overloading the server and impacting the performance of other cron jobs or the Odoo instance as a whole.

To configure this setting, you can add the following line to your odoo.conf file:

limit_time_real_cron = 60

This will limit the maximum execution time for each cron job to 60 seconds in real time. You can adjust this value based on the needs of your specific setup.

As for running multiple cron jobs simultaneously with heavy data, it's generally best to optimize the individual cron jobs to run as efficiently as possible. This can involve using more efficient algorithms, reducing the amount of data processed in each job, or using a more powerful server to handle the increased workload.

It's also a good idea to monitor the performance of your cron jobs and make adjustments as needed to ensure that they are running smoothly without impacting the overall performance of your Odoo instance.