Hi @elhay,
The previous thread was here; we generally close inactive threads after a couple of weeks.
This is more of a MySQL question than an OJS question, so you might have better luck on e.g. StackOverflow. In a nutshell, though, MySQL usually supports two storage engines: InnoDB and MyISAM. MyISAM is older and used to be the default, but nowadays the default is InnoDB.
If your OJS installation has been upgraded a few times, and your MySQL was also upgraded over that time, it’s possible that your database may be stored using MyISAM, or even a mix of MyISAM and InnoDB. In those cases, it’s important to convert the database over to InnoDB.
Have a look e.g. at this Q&A:
https://stackoverflow.com/questions/3856435/how-to-convert-all-tables-from-myisam-into-innodb
Regards,
Alec Smecher
Public Knowledge Project Team