Change a global variable and persist it

Command

SET PERSIST innodb_buffer_pool_size = 4294967296;

What it does

Sets the variable both on the running server and persistently across restarts (mysqld-auto.cnf).

When to use it

To change a server variable permanently without a restart.

Caution

SET PERSIST is a MySQL 8.0+ feature; MariaDB does not support it (there, edit my.cnf and restart). Use SET GLOBAL for a runtime-only change. Restart-only variables require SET PERSIST_ONLY.