[ERROR] /usr/sbin/mysqld: Can't open file: './database/table.frm' (errno: 24)
If you are facing this irritating problem, which not only took me hours to figure it out but also caused a little panic because it wasn't fixed although I rebooted the MySQL and the server itself - do not worry as this can be fixed very easily!
To fix this error, simply add the following setting to your my.cnf file:
open_files_limit = 8196 or any higher value.
This error happened to me when I was performing a database check on the server, which one of the cache tables in Drupal exhausted the MySQL resource usage. Just because of that, it causes MySQL to malfunction and affect the rest of the database as well.
So, once you set the value, just restart MySQL and you're good to go!
It's best to perform a database check again just to ensure it's all repaired and optimized.