Connection pooling in java with oracle
Database Resident Connection Pool (DRCP) is a connection pool in the server that is shared across many clients. You should use DRCP in connection pools where the number of active connections is fairly less than the number of open connections. As the number of instances of connection pools that can share the connections from DRCP pool increases, the benefits derived from using DRCP increases. DRCP increases Database server scalability and resolves the resource wastage issue that is associated with middle-tier connection pooling.
This chapter contains the following sections:
23.1 Overview of Database Resident Connection Pooling
In middle-tier connection pools, every connection cache maintains a minimum number of connections to the server. Each connection represents used up resources at the server. All these open connections are not utilized at any given time, which means that there are unused resources that unnecessarily take up server resources. In a multiple middle-tier scenario, these connections are not shared with any other middle tier and are retained in the cache even if some of these are idle. However, a large number of such middle-tier connection pools increase the number of inactive connections to the Database server significantly and waste a lot of Database resources because all the connections do not remain active simultaneously.
For example, in a middle-tier connection pool, if the minimum pool size is 200, then the connection pool has 200 connections to the server, and the Database server has 200 server processes associated with these connections. If there are 30 middle tiers with a connection pool of minimum size 200, then the server has 6000 (200 * 30) corresponding server processes running. Typically, on an average only 5% of the connections, and in turn, server processes are in use at any given time. So, out of the 6,000 server processes, only 300 server processes are active at any given time. This leads to over 5,700 unused server processes on the server. These unused processes are the wasted resources on the server.
The Database Resident Connection Pool implementation creates a pool on the server side, which is shared across multiple client pools. This significantly lowers memory consumption on the server because of reduced number of server processes on the server and increases the scalability of the Database server.