Data access tuning parameters

 

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Overview

For better application performance, you can tune some data access resources through the WAS console.

Tune these properties of data sources and connection pools to optimize the performance of transactions between your application and datastore.

 

Data source tuning

From the console, go to...

Resources | JDBC Providers | JDBC_provider | Data sources | datasource | WebSphere Application Server connection properties

Enable JMS one phase optimization support

If your application does not use JMS messaging, do not select this option.

Enabling...

1. Optimizes connections to the data source
2. Prevents JDBC applications from obtaining connections from the data source

Statement cache size

Specifies the number of statements that can be cached per connection. The WAS data source optimizes the processing of prepared statements and callable statements by caching those statements that are not being used in an active connection. Both statement types help reduce overhead for transactions with backend data.

• A prepared statement is a precompiled SQL statement that is stored in a PreparedStatement object. Application Server uses this object to run the SQL statement multiple times, as required by your application run time, with values that are determined by the run time.

• A callable statement is an SQL statement that contains a call to a stored procedure, which is a series of precompiled statements that perform a task and return a result. The statement is stored in the CallableStatement object. Application Server uses this object to run a stored procedure multiple times, as required by your application run time, with values that are determined by the run time.

In general, the more statements your application has, the larger the cache should be. Be aware, however, that specifying a larger statement cache size than needed wastes application memory and does not improve performance.

Determine the value for your cache size by adding the number of uniquely prepared statements and callable statements (as determined by the SQL string, concurrency, and the scroll type) for each application that uses this data source on a particular server. This value is the maximum number of possible statements that can be cached on a given connection over the life of the server.

Default: For most databases the default is 10. Zero means there is no cache statement.

Connection pool tuning

Resources | JDBC Providers | JDBC_provider | Data sources | data_source | Connection pool settings

Maximum connections

Specifies the maximum number of physical connections that can be created in this pool. These are the physical connections to the backend datastore. When this number is reached, no new physical connections are created; requestors must wait until a physical connection that is currently in use is returned to the pool.

For optimal performance, set the value for the connection pool lower than the value for the Web container threadpool size. Lower settings, such as 10 to 30 connections, might perform better than higher settings, such as 100.

Default: 10

Minimum connections

Specifies the minimum number of physical connections to maintain. Until this number is exceeded, the pool maintenance thread does not discard physical connections.

If you set this property for a higher number of connections than your application ultimately uses at run time, you do not waste application resources. WAS does not create additional connections to achieve your minimum setting. Of course, if your application requires more connections than the value you set for this property, application performance diminishes as connection requests wait for fulfillment.

Default: 1

Related tasks

Reference topic