Large queries on MyISAM tables crashing MySQL I have a PHP website, which is using the third-party software ResourceSpace, that when I installed it, it used my default storage engine to create the tables, which at the time was MyISAM. Now that the site has grown very large in size, I have started to see performance on my MySQL server slow down, and due to the intense queries that ResourceSpace runs, the site will start having issues loading pages due to very long running queries.  When I login to MySQL, I will see multiple of the same queries running for very long amounts of time (300+ seconds), with most having the state of 'Waiting on table level lock'. The queries will never finish, and I either have to kill them, kill MySQL, or MySQL itself will completely crash. Has anyone ever seen behavior like this with this particular software or any PHP website in general? 

Also, I am considering converting the engine on the tables over to InnoDB. I was wondering if there is any considerable risk with altering the tables and setting the engine to InnoDB?
I altered each of the tables that was using MyISAM as the engine, and the query time greatly decreased.  My site has also stopped locking up and responds much quicker during peek usage times.