## lifecycle interceptor 

 A type of interceptor  supported by Connector/J . It involves implementing the interface com.mysql.jdbc.ConnectionLifecycleInterceptor . See Also Connector/J, interceptor. 

## list 

 The InnoDB buffer pool  is represented as a list of memory pages . The list is reordered as new pages are accessed and enter the buffer pool, as pages within the buffer pool are accessed again and are considered newer, and as pages that are not accessed for a long time are evicted  from the buffer pool. The buffer pool is divided into sublists , and the replacement policy is a variation of the familiar LRU  technique. See Also buffer pool, eviction, LRU, page, sublist. 

## load balancing 

 A technique for scaling read-only connections by sending query requests to different slave servers in a replication or Cluster configuration. With Connector/J , load balancing is enabled through the com.mysql.jdbc.ReplicationDriver  class and controlled by the configuration property loadBalanceStrategy . See Also Connector/J, J2EE. 

## localhost 

See Also connection. 

## lock 

 The high-level notion of an object that controls access to a resource, such as a table, row, or internal data structure, as part of a locking  strategy. For intensive performance tuning, you might delve into the actual structures that implement locks, such as mutexes  and latches . See Also latch, lock mode, locking, mutex. 

## lock escalation 

 An operation used in some database systems that converts many row locks  into a single table lock , saving memory space but reducing concurrent access to the table. InnoDB  uses a space-efficient representation for row locks, so that lock  escalation is not needed. See Also locking, row lock, table lock. 

## lock mode 

 A shared (S) lock  allows a transaction  to read a row. Multiple transactions can acquire an S lock on that same row at the same time. 

An exclusive (X) lock allows a transaction to update or delete a row. No other transaction can acquire any kind of lock on that same row at the same time. 

Intention locks  apply to the table, and are used to indicate what kind of lock the transaction intends to acquire on rows in the table. Different transactions can acquire different kinds of intention locks on the same table, but the first transaction to acquire an intention exclusive (IX) lock on a table prevents other transactions from acquiring any S or X locks on the table. Conversely, the first transaction to acquire an intention shared (IS) lock on a table prevents other transactions from acquiring any X locks on the table. The two-phase process allows the lock requests to be resolved in order, without blocking locks and corresponding operations that are compatible. See Also intention lock, lock, locking, transaction. 

## locking 

 The system of protecting a transaction  from seeing or changing data that is being queried or changed by other transactions. The locking  strategy must balance reliability and consistency of database operations (the principles of the ACID  philosophy) against the performance needed for good concurrency . Fine-tuning the locking strategy often involves choosing an isolation level  and ensuring all your database operations are safe and reliable for that isolation level. 

