When a master server shuts down and restarts, its MEMORY (HEAP) tables become empty. To replicate this effect to slaves, the first time that the master uses a given MEMORY table after startup, it logs an event that notifies slaves that the table must to be emptied by writing a DELETE statement for that table to the binary log.

When a slave server shuts down and restarts, its MEMORY tables become empty. This causes the slave to be out of synchrony with the master and may lead to other failures or cause the slave to stop. For example, INSERT INTO ... SELECT FROM memory_table may insert a different set of rows on the master and slave.

The safe way to restart a slave that is replicating MEMORY tables is to first drop or delete all rows from the MEMORY tables on the master and wait until those changes have replicated to the slave. Then it is safe to restart the slave.

See Section 13.4, “The MEMORY (HEAP) Storage Engine”, for more information about MEMORY tables.