Sun Microsystems 820434310 manual Pool Size Settings, Timeout Settings, 4Connection Pool Sizing

Initial and Mimimum Pool Size

■ “Timeout Settings” on page 78

■ “Isolation Level Settings” on page 79

■ “Connection Validation Settings” on page 79

	Pool Size Settings
	The following settings control the size of the connection pool:
Initial and	Size of the pool when created, and its minimum allowable size.
Mimimum Pool
Size
Maximum Pool	Upper limit of size of the pool.
Size
Pool Resize	Number of connections to be removed when the idle timeout expires. Connections that have idled for
Quantity	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 3–4Connection Pool Sizing

Connection pool	Pros	Cons
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.	Slower access on the connection table.
	Requests will spend less (or no) time in the
	queue

Timeout Settings

There are two timeout settings:

■Max Wait Time: Amount of time the caller (the code requesting a connection) will wait before getting a connection timeout. The default is 60 seconds. A value of zero forces caller to wait indefinitely.

To improve performance set Max Wait Time to zero (0). This essentially blocks the caller thread until a connection becomes available. Also, this allows the server to alleviate the task of tracking the elapsed wait time for each request and increases performance.

78 Sun GlassFish Enterprise Server 2.1 Performance Tuning Guide • January 2009