PostgreSQL
PostgreSQL 7.2.x is to be installed on your choice of server platform. I have removed my Mac OS X install (small HD...) so I have not tested Mac OS X as a database server behind Tomcat and Apache.
Tip: On Redhat Linux where PostgreSQL is already installed download all the required RPMs of the latest version to a convenient directory.
su
cd directory_with_rpms
rpm -Uvh postgres*
Will upgrade PostgreSQL taking care of all required dependencies.
Get the latest developpement JDBC driver that is recommended on http://jdbc.postgresql.org and install it in /var/tomcat4/common/lib/postgresql.jar on your application server.
Modify /var/lib/pgsql/data/pg_hba.conf as per the instructions.
# If you want to allow non-local connections, you will need to
add more
# "host" records. Also, remember IP connections are only enabled
if you
# start the postmaster with the -i option.
Start the server and test connections. I would run one other application on the database server - Webmin. Make sure to connect over SSL. The PostgreSQL module will permit basic GUI manipulation. It also makes general maintenance of the database server more comfortable.
Redhat Database can be used as an alternative. It is PostgreSQL with Redhat administration tools. This alternative is recommended for organisations which require vendor aftersales support.