Java Persistence API (JPA)

OpenJPA is the default persistence provider in WAS.

Increasing the integer value of [com.ibm.websphere.jpa.entitymanager.poolcapacity] might improve performance by reducing the number of EntityManager instances that must be created. However, increasing the value affects the amount of consumed memory (http://pic.dhe.ibm.com/infocenter/wasinfo/v8r5/topic/com.ibm.websphere.nd.multiplatform.doc/ae/rejb_jpa_system_prop.html).

OpenJPA

If an OpenJPA application is running in a single JVM, then you may use the OpenJPA data cache: http://pic.dhe.ibm.com/infocenter/wasinfo/v8r5/topic/com.ibm.websphere.nd.multiplatform.doc/ae/tejb_datcacheconfig.html

Otherwise, you may use the OpenJPA second level (L2) cache provider plug-in over Dynacache: http://pic.dhe.ibm.com/infocenter/wasinfo/v8r5/topic/com.ibm.websphere.nd.multiplatform.doc/ae/rdyn_openjpa.html

L2 caching increases the memory consumption of the application, therefore, it is important to limit the size of the L2 cache. There is also a possibility of stale data for updated objects in a clustered environment. Configure L2 caching for read-mostly, infrequently modified entities. L2 caches are not recommended for frequently and concurrently updated entities.

If the application has a set of data that is used in a static, read-only method, like accessing basic persistent fields and persisting unidirectional relationships to a read-only type, then the WSJPA ObjectCache is a non-distributed cache of read-only entities that operates at the EntityManagerFactory object level: http://pic.dhe.ibm.com/infocenter/wasinfo/v8r5/topic/com.ibm.websphere.nd.multiplatform.doc/ae/tejb_jpaobjectcache.html

To trace all OpenJPA initiated SQL statements, edit persistence.xml and add a property with name "openjpa.Log" and value "SQL=TRACE". This will go to SystemErr.log:

[1/5/10 5:20:27:063 CST] 00000034 SystemErr     R 1293127  GTIMSPersistence  TRACE  [WebContainer : 5] openjpa.jdbc.SQL - <t 292426094, conn 2131263240>
[1730 ms] spent

Now look for the corresponding query, i.e. the statement corresponding to connection "conn 2131263240". The duration of the query in this case was 1730ms above.

[1/5/10 5:20:25:333 CST] 00000034 SystemErr     R 1291397  GTIMSPersistence  TRACE  [WebContainer : 5] openjpa.jdbc.SQL - <t 292426094, conn 2131263240>
executing prepstmnt 393222 select doc_Id from (SELECT d.doc_Id FROM GTIMS.Doc_Component_Instance d where d.doc_Component_Id = ? and d.document_Component_Inst_Data=?
intersect SELECT d.doc_Id FROM GTIMS.Doc_Component_Instance d where d.doc_Component_Id = ? and d.document_Component_Inst_Data=?)  where doc_Id!=?
[params=(long) 2, (String) -1761467286, (long) 1, (String) CORPORATION, (long) 82305]

Latest JPA performance options available in WAS 8.5 (https://www.ibm.com/developerworks/community/files/basic/anonymous/api/library/cfa136f0-30c1-4177-9901-62c05d900c5f/document/31f45287-2e71-41aa-aa0e-ace8400e0412/media):

<property name="openjpa.ConnectionRetainMode" value="always"/>
<property name="wsjpa.FastPath" value="true"/>
<property name="openjpa.RestoreState" value="false"/>
<property name="openjpa.OptimizeIdCopy" value="true"/>
<property name="openjpa.ProxyManager" value="delayCollectionLoading=true"/>