This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Connection pool is the group of connection objects.You can implment your own connection pool or can use application servers connection pool.At the start up ,server creates connection pool with connection objects.You can specify pool size. Whenever you make database transaction ,connection object from pool is used.Once your transaction is over object is returned to the pool.