[when configured appropriately, Apache] looks if the 
environment variable GATEWAY_INTERFACE starts with 
'CGI-Perl' and if the module Apache::DBI has been loaded. 
In this case every connect request will be forwarded to the
Apache::DBI module. This looks if a database handle from a
previous connect request is already stored and if this 
handle is still valid using the ping method. If these two 
conditions are fulfilled it just returns the database 
handle. The parameters defining the connection have to be 
exactly the same, including the connect attributes ! 
If there is no appropriate database handle or if the 
ping method fails, a new connection is established and 
the handle is stored for later re-use