The InnoDB shutdown mode. If the value is "SLOW", InnoDB does a slow
shutdown, a full purge and a change buffer merge before shutting
down. If the value is "FAST", InnoDB skips these operations at shutdown,
a process known as a fast shutdown. If the value is "IMMEDIATE", InnoDB
flushes its logs and shuts down cold, as if MySQL had crashed; no
committed transactions are lost, but the crash recovery operation makes
the next startup take longer.
The slow shutdown can take minutes, or even hours in extreme cases where
substantial amounts of data are still buffered. Use the slow shutdown
technique before upgrading or downgrading between MySQL major releases,
so that all data files are fully prepared in case the upgrade process
updates the file format.
The InnoDB shutdown mode. If the value is "SLOW", InnoDB does a slow shutdown, a full purge and a change buffer merge before shutting down. If the value is "FAST", InnoDB skips these operations at shutdown, a process known as a fast shutdown. If the value is "IMMEDIATE", InnoDB flushes its logs and shuts down cold, as if MySQL had crashed; no committed transactions are lost, but the crash recovery operation makes the next startup take longer.
The slow shutdown can take minutes, or even hours in extreme cases where substantial amounts of data are still buffered. Use the slow shutdown technique before upgrading or downgrading between MySQL major releases, so that all data files are fully prepared in case the upgrade process updates the file format.