Creating a database connection pool

Question

Need information on creating a connection pool to the database (irrespective of the database) , and how efficient they are? What are the conditions where they can enhance pe

Answer 1

The intro page to Apache DBCP sums it up nicely:

Creating a new connection for each user can be time consuming (often requiring multiple seconds of clock time), in order to perform a database transaction that might take milliseconds. Opening a connection per user can be unfeasible in a publicly-hosted Internet application where the number of simultaneous users can be very large. Accordingly, developers often wish to share a "pool" of open connections between all of the application's current users. The number of users actually performing a request at any given time is usually a very small percentage of the total number of active users, and during request processing is the only time that a database connection is required. The application itself logs into the DBMS, and handles any user account issues internally.

How efficient are they ? Depends on the implementation. Typically I would expect a pool to instantiate connections either at start-up or on request. The first connection will require a real connection to the database, and thereafter when you request a connection, you're given an existing pooled connection. So the first connection request will take the most time, and afterwards you're just pulling objects from a collection (very fast).