A new policy change will be enacted for all accounts on Wednesday, February 20th.  Those that remain over disk quota for more than one week will have insert privileges revoked.  This will have no effect on those already over quota or those who are in danger of going over quota.  Accounts that have gone over quota for a week, managed to miraculously not notice the sudden stoppage of e-mail, and database errors, but eventually freed up space will need to visit MySQL Manager in the control panel to enable INSERT and UPDATE privileges on the accounts.

This policy has been introduced to counteract the terrible threading issues in MySQL, which have been present as far back as 4.0.  Flash forward a few years later and it’s still an obscure bug that hits randomly.  When an INSERT or UPDATE statement occurs MySQL attempts to acquire an exclusive lock on the table to safeguard against corruption; however, this lock to used solely with writes trickles out past the table level, past the database level, and locks all tables in all databases.  Regardless whether it is a read or write operation, it’s locked.  Although I have written a monitoring service to check against these locks every 3 minutes and restart as necessary, I feel it is inadequate at addressing the problem head-on.  The new policy change should make lock-ups extremely infrequent (1 per 180+ days across all servers).  Right now we’re seeing them still happen at a rate of 1 per 30 days amongst all servers.

Again just to rehash: if you run over quota for more than a week, visit MySQL Manager after fixing disk space usage to re-enable the INSERT and UPDATE privileges.

Quota Overage -> Disable MySQL Insert/Update Policy Change