S SX X S Compatible Compatible Conflict SX Compatible Conflict Conflict X Conflict Conflict Conflict •An  sx-lock  provides write access to a common resource while permitting inconsistent reads by other threads. sx-locks  were introduced in MySQL 5.7 to optimize concurrency and improve scalability for read-write workloads. •An  x-lock  provides write access to a common resource while not permitting inconsistent reads by other threads. •An  s-lock  provides read access to a common resource. The following matrix summarizes rw-lock type compatibility. See Also latch, lock, mutex, Performance Schema.  Savepoints help to implement nested  transactions . They can be used to provide scope to operations on tables that are part of a larger transaction. For example, scheduling a trip in a reservation system might involve booking several different flights; if a desired flight is unavailable, you might  roll back  the changes involved in booking that one leg, without rolling back the earlier flights that were successfully booked. See Also rollback, transaction.  The ability to add more work and issue more simultaneous requests to a system, without a sudden drop in performance due to exceeding the limits of system capacity. Software architecture, hardware configuration, application coding, and type of workload all play a part in scalability. When the system reaches its maximum capacity, popular techniques for increasing scalability are  scale up  (increasing the capacity of existing hardware or software) and  scale out  (adding new servers and more instances of MySQL). Often paired with  availability  as critical aspects of a large-scale deployment. See Also availability, scale out, scale up.  A technique for increasing  scalability  by adding new servers and more instances of MySQL. For example, setting up replication, NDB Cluster, connection pooling, or other features that spread work across a group of servers. Contrast with  scale up . See Also scalability, scale up.  A technique for increasing  scalability  by increasing the capacity of existing hardware or software. For example, increasing the memory on a server and adjusting memory-related parameters such as innodb_buffer_pool_size  and  innodb_buffer_pool_instances . Contrast with  scale out See Also scalability, scale out.  Conceptually, a schema is a set of interrelated database objects, such as tables, table columns, data types of the columns, indexes, foreign keys, and so on. These objects are connected through SQL syntax, because the columns make up the tables, the foreign keys refer to tables and columns, and so on. Ideally, they are also 6184 schema scale up scale out scalability savepoint S