JBoss.org Community Documentation
The number of connections in the pool is controlled by the pool sizes.
<min-pool-size/> - When the number of connections falls below this size, new connections are created
<max-pool-size/> - No more than this number of connections are created
<prefill/> - Feature Request has been implemented for 4.0.5. Note: the only pooling strategy that supports this feature is OnePool?, or ByNothing? pooling criteria.
The pool filling is done by a separate "Pool Filler" thread rather than blocking application threads.