Databases Reference
In-Depth Information
connections to Sybase and Microsoft SQL Server, and a pool will exist for
henv2
that has connections to Oracle and DB2.
We have included this configuration option here for completeness; however,
it would be unusual to configure your application to use many environ-
ments.
In the ODBC model as defined in the ODBC specification, you can't define a
minimum and a maximum pool size, which can cause resource issues because
the connections, even when not in use, hold onto resources. Holding these
resources can affect performance by limiting their availability to other threads or
processes. The size of the pool is limited only by memory or licensing constraints
on the server.
Even with this limitation in the ODBC connection pool model, you will
want to use connection pooling when you have the following:
•
A middle-tier application that connects over a network
•
An application that repeatedly connects and disconnects, such as an Internet
application
Connection pooling in ADO.NET isn't provided by the core components of the
.NET Framework. If present, it must be implemented in the ADO.NET data
provider. The most popular and widely used implementation is discussed in this
section.
In ADO.NET, a connection pool is associated with a specific connection
string. A connection pool is created for each connection request that uses a
unique connection string. For example, if an application requests two connec-
tions over its lifetime using the following two connection strings, two connection
pools are created, one for each connection string:
Host=Accounting;Port=1521;User ID=scott;Password=tiger;
Service Name=ORCL;
Host=Accounting;Port=1521;User ID=sam;Password=lion21;
Service Name=ORCL;
