Sun Java System Application Server Enterprise Edition 8.1 2005Q2 Performance Tuning Guide

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## Improving Performance of EJB Transactions

This section provides some tips to improve performance when using transactions.

### Use Container-Managed Transactions

Container-managed transactions are preferred for consistency, and provide better performance.

### Don’t Encompass User Input Time

To avoid resources being held unnecessarily for long periods, a transaction should not encompass user input or user think time.

### Identify Non-Transactional Methods

Declare non-transactional methods of session EJB components with `NotSupported` or `Never` transaction attributes. These attributes can be found in the `ejb-jar.xml` deployment descriptor file. Transactions should span the minimum time possible since they lock database rows.

### Use TX_REQUIRED for Long Transaction Chains

For very large transaction chains, use the transaction attribute `TX_REQUIRED.` To ensure EJB methods in a call chain, use the same transaction.

### Use Lowest Cost Database Locking

Use the lowest cost locking available from the database that is consistent with any transaction. Commit the data after the transaction completes rather than after each method call.

### Use XA-Capable Data Sources Only When Needed

When multiple database resources, connector resources or JMS resources are involved in one transaction, a distributed or global transaction needs to be performed. This requires XA capable resource managers and data sources. Use XA capable data sources, only when two or more data source are going to be involved in a transaction. If a database participates in some distributed transactions, but mostly in local or single database transactions, it is advisable to register two separate JDBC resources and use the appropriate resource in the application.

### Configure JDBC Resources as One-Phase Commit Resources

To improve performance of transactions involving multiple resources, the Application Server uses last agent optimization (LAO), which allows the configuration of one of the resources in a distributed transaction as a one-phase commit (1PC) resource. Since the overhead of multiple-resource transactions is much higher for a JDBC resource than a message queue, LAO substantially improves performance of distributed transactions involving one JDBC resource and one or more message queues. To take advantage of LAO, configure a JDBC resource as a 1PC resource. Nothing special needs to be done to configure JMS resources.

In global transactions involving multiple JDBC resources, LAO will still improve performance, however, not as much as for one JDBC resource. In this situation, one of the JDBC resources should be configured as 1PC, and all others should be configured as XA.

### Use the Least Expensive Transaction Attribute

Set the following transaction attributes in the EJB deployment descriptor file (`ejb-jar.xml`). Options are listed from best performance to worst. To improve performance, choose the least expensive attribute that will provide the functionality your application needs:

1. NEVER

2. TX_NOTSUPPORTED

3. TX_MANDATORY

4. TX_SUPPORTS

5. TX_REQUIRED

6. TX_REQUIRESNEW

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