inverted index 

 A data structure optimized for document retrieval systems, used in the implementation of InnoDB full-text search . The InnoDB FULLTEXT index , implemented as an inverted index, records the position of each word within a document, rather than the location of a table row. A single column value (a document stored as a text string) is represented by many entries in the inverted index. See Also full-text search, FULLTEXT index, ilist. 

IOPS 

 Acronym for I/O operations per second . A common measurement for busy systems, particularly OLTP applications. If this value is near the maximum that the storage devices can handle, the application can become disk-bound , limiting scalability . See Also disk-bound, OLTP, scalability. 

isolation level 

 One of the foundations of database processing. Isolation is the I  in the acronym ACID ; the isolation level is the setting that fine-tunes the balance between performance and reliability, consistency, and reproducibility of results when multiple transactions  are making changes and performing queries at the same time. 

From highest amount of consistency and protection to the least, the isolation levels supported by InnoDB are: SERIALIZABLE , REPEATABLE READ , READ COMMITTED , and READ UNCOMMITTED . 

With InnoDB  tables, many users can keep the default isolation level ( REPEATABLE READ ) for all operations. Expert users might choose the READ COMMITTED  level as they push the boundaries of scalability with OLTP processing, or during data warehousing operations where minor inconsistencies do not affect the aggregate results of large amounts of data. The levels on the edges ( SERIALIZABLE  and READ UNCOMMITTED ) change the processing behavior to such an extent that they are rarely used. See Also ACID, OLTP, READ COMMITTED, READ UNCOMMITTED, REPEATABLE READ, SERIALIZABLE, transaction. 

J 

J2EE 

 Java Platform, Enterprise Edition: Oracle’s enterprise Java platform. It consists of an API and a runtime environment for enterprise-class Java applications. For full details, see http://www.oracle.com/technetwork/java/ javaee/overview/index.html. With MySQL applications, you typically use Connector/J  for database access, and an application server such as Tomcat  or JBoss  to handle the middle-tier work, and optionally a framework such as Spring . Database-related features often offered within a J2EE stack include a connection pool  and failover support. 

See Also connection pool, Connector/J, failover, Java, JBoss, Spring, Tomcat. 

Java 

 A programming language combining high performance, rich built-in features and data types, object-oriented mechanisms, extensive standard library, and wide range of reusable third-party modules. Enterprise development is supported by many frameworks, application servers, and other technologies. Much of its syntax is familiar to C and C++  developers. To write Java applications with MySQL, you use the JDBC  driver known as Connector/J . See Also C, Connector/J, C++, JDBC. 

JBoss 

See Also J2EE. 

JDBC 

 Abbreviation for “Java Database Connectivity” , an API  for database access from Java  applications. Java developers writing MySQL applications use the Connector/J  component as their JDBC driver. 

