Oracle C++ Call Interface Programmer's Guide

Connecting to a Database
duration. Opening a connection to the database for every thread would result in
inefficient utilization of connections and poor performance.
By employing the connection pooling feature, your application can use database
management system (DBMS) functionality to manage the connections. Oracle
creates a small number of open connections, dynamically selects one of the free
connections to execute a statement, and then releases the connection immediately
after the execution. This relieves you from creating complex mechanisms to handle
connections and optimizes performance in your application.
Creating a Connection Pool
To create a connection pool, you use the createConnectionPool method:
virtual ConnectionPool* createConnectionPool(
const string &poolUserName,
const string &poolPassword,
const string &connectString ="",
unsigned int minConn =0,
unsigned int maxConn =1,
unsigned int incrConn =1) = 0;
The following parameters are used in the previous method example:
■ poolUserName: The owner of the connection pool
■ poolPassword: The password to gain access to the connection pool
■ connectString ="": The database name that specifies the database server to
which the connection pool is related
■ minConn: The minimum number of connections to be opened when the
connection pool is created
■ maxConn: The maximum number of connections that can be maintained by the
connection pool. When the maximum number of connections are open in the
connection pool, and all the connections are busy, an OCCI method call that
needs a connection waits until it gets one, unless setErrorOnBusy() was called
on the connection pool
■ incrConn: The additional number of connections to be opened when all the
connections are busy and a call needs a connection. This increment is
implemented only when the total number of open connections is less than the
maximum number of connections that can be opened in that connection pool
The following code example demonstrates how you can create a connection pool:
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