When a transaction is waiting for a resource, it will wait for the resource to become free, or stop waiting and return with the error

ERROR HY000: Lock wait timeout exceeded; try restarting transaction

Before InnoDB Plugin 1.0.2, the only way to set this parameter was in the MySQL option file (my.cnf or my.ini), and changing it required shutting down and restarting the server. Beginning with the InnoDB Plugin 1.0.2, the configuration parameter innodb_lock_wait_timeout can be set at runtime with the SET GLOBAL or SET SESSION commands. Changing the GLOBAL setting requires the SUPER privilege and affects the operation of all clients that subsequently connect. Any client can change the SESSION setting for innodb_lock_wait_timeout, which affects only that client.