Sun GlassFish Enterprise Server 2.1 Performance Tuning Guide

Pool Size Settings

The following settings control the size of the connection pool:

Initial and Mimimum Pool Size

Size of the pool when created, and its minimum allowable size.

Maximum Pool Size

Upper limit of size of the pool.

Pool Resize Quantity

Number of connections to be removed when the idle timeout expires. Connections that have idled for longer than the timeout are candidates for removal. When the pool size reaches the initial and minimum pool size, removal of connections stops.

The following table summarizes pros and cons to consider when sizing connection pools.

Table 3–4 Connection Pool Sizing

Connection pool  



Small Connection pool 

Faster access on the connection table. 

May not have enough connections to satisfy requests. 

Requests may spend more time in the queue. 

Large Connection pool 

More connections to fulfill requests. 

Requests will spend less (or no) time in the queue 

Slower access on the connection table.