Sun Java System Application Server 9.1 Deployment Planning Guide

Estimating Load on the HADB

To calculate load on the HADB, consider the following factors:

For instructions on configuring session persistence, see Chapter 8, Configuring High Availability Session Persistence and Failover, in Sun Java System Application Server 9.1 High Availability Administration Guide.

HTTP Session Persistence Frequency

The number of requests per minute received by the HADB depends on the persistence frequency. Persistence Frequency determines how often Application Server saves HTTP session data to the HADB.

The persistence frequency options are:

The following table summarizes the advantages and disadvantages of persistence frequency options.

Table 2–1 Comparison of Persistence Frequency Options

Persistence Frequency Option 




Guarantees that the most up-to-date session information is available. 

Potentially increased response time and reduced throughput. 


Better response time and potentially better throughput. 

Less guarantee that the most updated session information is available after the failure of an application server instance. 

HTTP Session Size and Scope

The session size per request depends on the amount of session information stored in the session.

Tip –

To improve overall performance, reduce the amount of information in the session as much as possible.

It is possible to fine-tune the session size per request through the persistence scope settings. Choose from the following options for HTTP session persistence scope:

To use this option, the application must:

Table 2–2 Comparison of Persistence Scope Options

Persistence Scope Option 




Provides improved response time for requests that do not modify session state. 

During the execution of a web method, typically doGet() or doPost(), the application must call a session method:

  • setAttribute() if the attribute was changed

  • removeAttribute() if the attribute was removed.


No constraint on applications. 

Potentially poorer throughput and response time as compared to the modified-session and the modified-attribute options.


Better throughput and response time for requests in which the percentage of session state modified is low. 

As the percentage of session state modified for a given request nears 60%, throughput and response time degrade. In such cases, the performance is worse than the other options because of the overhead of splitting the attributes into separate records. 

Stateful Session Bean Checkpointing

For SFSB session persistence, the load on HADB depends on the following:

Checkpointing generally occurs after any transaction involving the SFSB is completed (even if the transaction rolls back).

For better performance, specify a small set of methods for checkpointing. The size of the data that is being checkpointed and the frequency of checkpointing determine the additional overhead in response time for a given client interaction.