Percona Server has implemented variable which can be used for enforcing the use of a specific storage engine.
When this variable is specified and a user tries to create a table using an explicit storage engine that is not the specified enforced engine, he will get either an error if the NO_ENGINE_SUBSTITUTION SQL mode is enabled or a warning if NO_ENGINE_SUBSTITUTION is disabled and the table will be created anyway using the enforced engine (this is consistent with the default MySQL way of creating the default storage engine if other engines aren’t available unless NO_ENGINE_SUBSTITUTION is set).
In case user tries to enable enforce_storage_engine with engine that isn’t available, system will not start.
If you’re using enforce_storage_engine, you must either disable it before doing mysql_upgrade or perform mysql_upgrade with server started with --skip-grants-tables.
This variable is not case sensitive.