The optimal fetch size is not always obvious. In a typical EJB3.0 JPA application, a variety of factors affect when database transaction isolation levels apply and to what extent a particular database transaction isolation can be achieved, including the following: Database Login method setTransactionIsolation, See Also: "Shared and Isolated Cache" at http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Caching/Shared_and_Isolated. Note that this tool is intended for use with single-threaded finite use cases. Statement caching is used to lower the performance impact of repeated cursor creation and repeated statement parsing and creation; this can improve performance for applications using a database. However, not all databases and JDBC drivers support these options. Please see "Migrating from Native TopLink to EclipseLink" in the EclipseLink Solutions Guide for current information. Even if a query accesses the data source, if the objects corresponding to the records returned are in the cache, EclipseLink uses the cached objects. The type is set through the query hint "eclipselink.batch.type". By default, EclipseLink caches objects read from a data source. See Also: "Lazy Loading" at http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Basic_Mappings/Lazy_Basics, Default Value: On for collection mapping (ToMany mappings, @OneToMany, @ManyToMany), Default Value: Off for reference (ToOne mappings, @OneToOne, @ManyToOne), (Note that setting lazy loading On for @OneToOne, @ManyToOne requires weaving, which is On by default for Java Java EE.). You can specify whether a given query runs against the in-memory cache, the database, or both. Can also be set at entity level using @ReadOnly class annotation. EclipseLink defers reading the dependent object until you access that specific attribute. EclipseLink is full version of TopLink donated by Oracle to Eclipse foundation. This chapter focuses on tuning JPA in the context of EJB3.0 and a Java EE environment. Note that batching is only allowed on queries that have a single object in their select clause. Each test consisted of running the test in a single threaded loop and recording the number of operations in a set amount of time. The query cache is distinct from the object cache. EclipseLink can transform data between an object representation and a representation specific to a data source. For more information see: Section 8.3.1, "Cache Refreshing Scenarios", See Also: EclipseLink User's Guide section, "Configuring Cache Refreshing" and "How to Use the @Cache_Annotation". Being a specification, JPA must be implemented by reference implementers or as products like TopLink Essentials (reference implementation for JPA 1.x), Hibernate, OpenJPA, etc. So you can use JPA, and still get access to most of the TopLink functionality that goes beyond the JPA spec. The eclipselink.batch hint supplies EclipseLink with batching information so subsequent queries of related objects can be optimized in batches instead of being retrieved one-by-one or in one large joined read. Before you begin tuning, consider reviewing the introductory information found at the following: The EclipseLink JPA User's Guide at http://wiki.eclipse.org/EclipseLink/UserGuide/JPA, "Considering JPA Entity Architecture" at http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Introduction/Architecture, Introduction to EclipseLink Queries at http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Querying, Introduction to Cache at http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Caching, Introduction to Mapping and Configuration at http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping, For more information on Oracle TopLink, see the TopLink page on OTN http://www.oracle.com/technology/products/ias/toplink/index.html. Generally it is recommended that you leave caching enabled. This is the case when certain data in the application changes so frequently that it is desirable to always refresh the data, instead of only refreshing the data when a conflict is detected. EclipseLink is the intended path forward for persistence for Oracle and TopLink. If infrequent concurrent updates to the same rows are expected, then optimistic locking may provide the best performance while providing data consistency guarantees. In this tutorial, we'll be discussing Hibernate and the Java Persistence API (JPA) – with a focus on the differences between them. Use for queries of tables with columns mappings to table data you need.You should only use either batch-reading or joining if you know that you are going to access all of the data; if you do not intend to access the relationships, then just let indirection defer their loading. Without lazy loading on, when EclipseLink retrieves a persistent object, it retrieves all of the dependent objects to which it refers. Set through query hint "eclipselink.read-only". Joining is part of the JPA specification, whereas batch fetching is not. This is the case when certain data in the application changes so frequently that it is desirable to always refresh the data, instead of only refreshing the data when a conflict is detected. For entities that can be updated concurrently, consider using the locking policy to prevent a user from writing over another users changes. This provides support for very large L2 caches that span cluster nodes. In 2002,TopLink was acquired by Oracle Corporation and was developed under the Oracle Fusion Middleware product. This avoids the default behavior of retrieving the object from the database first and then for objects already in the cache, returning the cached values (not updated from the database access, unless refresh has been set on the query). Always use read-only for all read-only operations. A mapping corresponds to a single data member of a domain object. Full features of EclipseLink can be read in TopLink Essentials is a subset of … The Oracle JDBC driver supports this option. To get performance gains by avoiding the database lookup for objects already in the cache, you can configure that the search attempts to retrieve the required object from the cache first, and then search the data source only if the object is not in the cache. 8.1Introduction to the Solution Set this option in an Oracle Weblogic data-source by setting Statement Cached Type and Statement Cached Size configuration options. The different combinations have both functional and performance implications, but often the functional requirements for up-to-date data and data consistency lead to the settings for these options, even when it may be at the expense of performance. Statement caching is used to lower the performance impact of repeated cursor creation and repeated statement parsing and creation; this can improve performance for applications using a database. The persistence property in persistence.xml "eclipselink.jdbc.batch-writing"="JDBC" is used to configure this. Note that the Oracle JDBC driver bundled with Oracle Application Server does support this option. Table 9-2 shows the Entity relationship query parameters for performance tuning. Locking is set through JPA @Version annotation, eclipselink.read-only, See Also: "Introduction to EclipseLink Application Development - "Locking" at http://wiki.eclipse.org/Introduction_to_EclipseLink_Application_Development_(ELUG)#Locking, "Using EclipseLink JPA Extensions Pessimistic Lock" at http://wiki.eclipse.org/Introduction_to_EclipseLink_Application_Development_(ELUG)#Pessimistic_Locking, How to Use EclipseLink Locking at http://wiki.eclipse.org/EclipseLink/Examples/JPA/Locking, "Configuring Locking" at http://wiki.eclipse.org/Introduction_to_EclipseLink_JPA_(ELUG)#Configuring_Locking. The query cache is distinct from the object cache. The TopLink code was donated to the Eclipse Foundation and the EclipseLink project was born in 2007. This transformation is called mapping and it is the core of a EclipseLink project. See Also: "How to Use Result Set Pagination" at http://wiki.eclipse.org/Optimizing_the_EclipseLink_Application_(ELUG)#How_to_Use_Result_Set_Pagination_for_Optimization. To optimize performance for read-only entities, consider defining the entity as read-only or use a read-only query hint. For best performance, restore the logging levels to the default levels when you are done profiling or debugging. Oracle Fusion Middleware Configuring and Managing JDBC for Oracle WebLogic Server, http://wiki.eclipse.org/EclipseLink/Performance, http://wiki.eclipse.org/EclipseLink/FAQ/JPA/BestPractices, http://wiki.eclipse.org/Optimizing_the_EclipseLink_Application_(ELUG)#Introduction_to_Optimization, http://wiki.eclipse.org/Optimizing_the_EclipseLink_Application_(ELUG)#Optimizing_for_a_Production_Environment, http://wiki.eclipse.org/Introduction_to_Java_Persistence_API_(ELUG), http://wiki.eclipse.org/Introduction_to_EclipseLink_JPA_%28ELUG%29, http://wiki.eclipse.org/Introduction_to_EclipseLink_Application_Development_(ELUG)#Considering_JPA_Entity_Architecture, http://wiki.eclipse.org/Introduction_to_EclipseLink_Queries_(ELUG), http://wiki.eclipse.org/Introduction_to_Cache_(ELUG), http://wiki.eclipse.org/Introduction_to_EclipseLink_Mapping_and_Configuration_(ELUG), http://www.oracle.com/technology/products/ias/toplink/index.html, http://www.oracle.com/technology/products/ias/toplink/doc/11110/relnotes/toplink-relnotes.html#CHDGAEDJ, http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#Bind_Parameters, http://wiki.eclipse.org/Optimizing_the_EclipseLink_Application_(ELUG)#How_to_Use_Batch_Writing_for_Optimizatio, http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#Using_EclipseLink_JPA_Extensions_for_Tracking_Changes, http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#Read_OnlyUsing_EclipseLink_JPA_Extension, http://wiki.eclipse.org/Optimizing_the_EclipseLink_Application_(ELUG)#How_to_Use_Result_Set_Pagination_for_Optimization, http://wiki.eclipse.org/Optimizing_the_EclipseLink_Application_(ELUG)#Sequence_Number_Preallocation, http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#Batch, http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#Join_Fetch, http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#What_You_May_Need_to_Know_About_EclipseL, http://wiki.eclipse.org/Introduction_to_Cache_(ELUG)#Session_Cache, http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#Table_19-13, http://wiki.eclipse.org/Introduction_to_EclipseLink_Queries_%28ELUG%29#How_to_Cache_Query_Results_in_the_Query_, http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#How_to_Use_EclipseLink_JPA_Query_Hints, http://wiki.eclipse.org/EclipseLink/FAQ/JPA/BestPractices#M3._Configure_the_Cache, http://wiki.eclipse.org/Introduction_to_EclipseLink_Application_Development_(ELUG)#Locking, http://wiki.eclipse.org/Introduction_to_EclipseLink_Application_Development_(ELUG)#Pessimistic_Locking, http://wiki.eclipse.org/EclipseLink/Examples/JPA/Locking, http://wiki.eclipse.org/Introduction_to_EclipseLink_JPA_(ELUG)#Configuring_Locking, http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#Cache_Usage, http://wiki.eclipse.org/Using_Advanced_Unit_of_Work_API_(ELUG)#Database_Transaction_Isolation_Levels, Section 8.3.1, "Cache Refreshing Scenarios", http://wiki.eclipse.org/Http:/wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#Read_OnlyUsing_EclipseLink_JPA_Extension, http://www.oracle.com/technology/products/ias/toplink/doc/11110/grid/tlgug003.htm, http://www.oracle.com/technology/products/ias/toplink/doc/11110/grid/toc.htm, http://wiki.eclipse.org/Configuring_a_Descriptor_(ELUG)#Configuring_Common_Descriptor_Options, http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#Using_EclipseLink_JPA_Extensions_for_Logging. Default Value: AttributeLevel if using weaving (J2EE default), otherwise Deferred. There is not a single tuning parameter that sets a particular database transaction isolation level in a JPA application that uses EclipseLink. Batch reading is more efficient than joining because it avoids reading duplicate data; therefore for best performance for queries where batch reading is supported, consider using batch reading instead of join reading. EclipseLink was initiated based on the contribution of Oracle TopLink. If you have an object that is always read from the database, as in a pessimistic locked object, then the cache for that entity should be disabled. Table 9-1 and Table 9-2 show tuning parameters and performance recommendations related to SQL statements and querying. Besides results and conclusions, the full test code is also available in case you want to repeat the test yourself. The idea is that you write your application against interfaces on GF 3 and then you are able to deploy and use it in JBoss AS 6, for instance - this requires that you don't use any provider specific functionality. In the case when you want to avoid stale data, but getting stale data is not a major issue, then using a cache expiry policy would be the recommended solution. The default settings for EJB3.0/JPA used with the EclipseLink persistence manager and cache are no locking, no cache refresh, and cache-usage DoNotCheckCache. Going forward Oracle TopLink will include EclipseLink to deliver its core persistence functionality. This section lists a few features in EclipseLink that can help you analyze your JPA application performance: For profiling performance, see "Measuring EclipseLink Performance with the EclipseLink Profiler" in the EclipseLink User's Guide. Setting an EJB3.0 JPA Entity to read-only ensures that the entity cannot be modified and enables EclipseLink to optimize unit of work performance. To migrate your application to use the new code base, you must rename the packages in your code. This enables any query executed with the same parameters to obtain a query cache hit and return the same result set. This is how we had datasource set: All users have read access to the data. For information on Mapping see, "Optimizing Mappings and Descriptors" in the EclipseLink User Guide at http://wiki.eclipse.org/Optimizing_the_EclipseLink_Application_(ELUG)#Optimizing_Mappings_and_Descriptors. In a typical EJB3.0 JPA application, a variety of factors affect when database transaction isolation levels apply and to what extent a particular database transaction isolation can be achieved, including the following: Database Login method setTransactionIsolation, See Also: "Database Transaction Isolation Levels" at http://wiki.eclipse.org/Using_Advanced_Unit_of_Work_API_(ELUG)#Database_Transaction_Isolation_Levels. Use lazy loading for all mappings. Using parameterized SQL and prepared statement caching, you can improve performance by reducing the number of times the database SQL engine parses and prepares SQL for a frequently called query. See Also: "Using EclipseLink JPA Extensions - Fetch Size" at http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_(ELUG)#Bind_Parameters. The JDBC fetch size gives the JDBC driver a hint as to the number of rows that should be fetched from the database when more rows are needed. Oracle TopLink extends EclipseLink with advanced integration into the Oracle Application Server. Caching is enabled when the value of the persistence.xml caching element is ENABLE_SELECTIVE or DISABLE_SELECTIVE. Replace the default EclipseLink L2 cache with Coherence. EclipseLink defers reading the dependent object until you access that specific attribute. Default Value: Type SoftWeak, Size 100 (per Entity). The query cache is indexed by the query and the query parameters - not the object's primary key. To ensure that your application uses the cache and does not read stale data from the cache (when you do not have exclusive access), you must configure these and other isolation related settings appropriately. When a user attempts to make a change, the application checks to ensure the data has not changed since the user read the data. For more information on using @Partioned and other partitioning policy annotations, see "Data Partitioning" at http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Advanced_JPA_Development/Data_Partitioning. You can specify whether a given query runs against the in-memory cache, the database, or both. This section covers using efficient SQL statements and SQL querying. With TopLink Grid, there are several types of integration with EclipseLink JPA features. Batch fetching can also be set using the @BatchFetch annotation. This default caching policy can lead to stale data in the application. The information in this chapter assumes that you are familiar with the basic functionality of EclipseLink. Oracle TopLink includes the open source EclipseLink as the Java Persistence API (JPA) implementation. Always consult your use case scenarios to determine which tuning parameters are appropriate for your environment. Set through query hint "eclipselink.read-only". 8 Migrating from Hibernate to EclipseLink. Can disable through persistence.xml properties "eclipselink.weaving". When using pessimistic locking at the entity level, it is recommended that you use it with an isolated cache (Shared=False) for best performance. For information on configuring and tuning an EclipseLink Entity Cache using Oracle Coherence, see Section 8.4, "Coherence Integration". Most JDBC drivers use a default fetch size of 10. The chapter includes the following topics: Section 8.1, "About Oracle TopLink and EclipseLink", Section 8.2, "Efficient SQL Statements and Queries", Section 8.3, "Cache Configuration Tuning", Section 8.5, "Mapping and Descriptor Configurations", Section 8.6, "Analyzing EclipseLink JPA Entity Performance", EclipseLink Performance Tuning at http://wiki.eclipse.org/EclipseLink/Performance, EclipseLink JPA Tuning Best Practices at http://wiki.eclipse.org/EclipseLink/FAQ/JPA/BestPractices, Introduction to Optimization at http://wiki.eclipse.org/Optimizing_the_EclipseLink_Application_(ELUG)#Introduction_to_Optimization. Use this feature to improve query performance by reducing database access. In addition to the object cache in EclipseLink, EclipseLink also supports a query cache: The object cache indexes objects by their primary key, allowing primary key queries to obtain cache hits. See Also: "Join Fetch" at http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Querying/Query_Hints#Join_Fetch, Use for queries of tables with columns mappings to table data you need.You should only use either batch fetching or joining if you know that you are going to access all of the data; if you do not intend to access the relationships, then just let indirection defer their loading.For the best performance of selects, where batch fetching is not supported, a join is recommended. Set at the entity level using @ReadOnly class annotation. The value of the Cacheable annotation is inherited by subclasses; it can be overridden by specifying Cacheable on a subclass. As part of the job, you'll be working with JPA, Java EE, EclipseLink, TopLink, GlassFish, WebLogic, JAX-B, JAX-WS and much, much more. For more information, see "Locking" at http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Mapping/Locking. Configure entities to execute queries in the Coherence data grid instead of the database. However, Hibernate was also the JPA implementation that executed the lowest number of queries, although the differences in this value (3080 for Hibernate vs 3740 for Toplink Essentials) are not so …

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