START TRANSACTION [ mode [, ...] ]

ISOLATION LEVEL { READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE }
READ { ONLY | WRITE }

START TRANSACTION;
START TRANSACTION ISOLATION LEVEL REPEATABLE READ;
START TRANSACTION READ WRITE;
START TRANSACTION ISOLATION LEVEL READ COMMITTED, READ ONLY;
START TRANSACTION READ WRITE, ISOLATION LEVEL SERIALIZABLE;