Persistent connections are implemented in PBMS by using pool connections.
A pool is defined as a group of connections opened to the same server using the same connection parameters.
The connections in the pool are persistent in that they do not close when the execution of your script ends or
when pbms_close() is called. Instead in both cases the connection is just released back to the pool to be
reused by the next call to pbms_connect() or pbms_pconnect() . Connections are only added to the pool by
opening them with pbms_pconnect() although pbms_connect() will use a connection from a pool if the
pool already exists and there is an unused connection in the pool.