When you first install the ATG platform, it is configured to use its own data sources (JDBC connection pools) and transaction manager. The data sources point to the SOLID demonstration database that is installed with ATG. This database contains the tables necessary for running ATG and the demo applications.
When you deploy your site, you should reconfigure your installation to use the data sources and transaction manager that your application server uses. While the SOLID database is suitable for evaluation and development; it is not designed for a high-volume site, and most application servers do not have drivers to support it.
Note that data sources for all application servers should always use the READ_COMMITTED isolation level (on DB2, use the equivalent CURSOR STABILITY).
