MySQL Error Message
You must raise the value of innodb_open_files in my.cnf!
Remember that InnoDB keeps all redo log files and all system
tablespace files open for the whole time mysqld is running, and
needs to open also some .ibd files if the file-per-table storage
model is used. Current open files %zu, max allowed open files %zu.
Reason for the Error
ER_IB_MSG_284 was added in 8.0.11.