Define connection pooling

You can use the Pooling option in the Database Connection dialog box to set up a connection pool and define options like the initial pool size, maximum pool size, and connection pool parameters. By default, a connection remains open for each individual report or set of reports in PUC and for each individual step in a transformation in PDI. For example, you might start by specifying a pool of ten or fifteen connections, and as you run reports in PUC or transformations in PDI, the unused connections drop off. Pooling helps control database access, especially if you have dashboards that contain many reports and require a large number of connections. Pooling can also be implemented when your database licensing restricts the number of active concurrent connections.

Perform the following steps to specify pooling options:

1. Open the Database Connection dialog box in PUC or PDI.

2. Click Pooling in the left pane.

   Options appear for your JDBC driver as shown in the example below:

   The following table shows an example of Pooling options that might be available in a typical JDBC driver. Check your driver documentation for driver-specific pooling details.

Option	Description
Enable Connection Pooling	Enables connection pooling.
Pool Size	Initial Set the initial size of the connection pool. Maximum Set the maximum number of connections in the connection pool.
Parameters	You can define additional custom pool parameters. Click on any parameter to view a short description of that parameter. Click Restore Defaults when to restore the default values for selected parameters. The most commonly-used parameter is validationQuery. The parameter differs slightly depending on your RDBMS connection. The basic set of Pentaho databases use the following values for validationQuery: For Oracle and PostgreSQL, use Select 1 from dual. For MS SQL Server and MySQL, use Select 1.
Description	Enter a description for your parameters.

3. Click **Test**.

A success message appears if the connection is established.

4. Click OK to close the connection test dialog box.

1. To save the connection, click OK to close the Database Connection dialog box.