doc for jdbc pool configuration

[Felix Schumacher]

Hi all,

in our documentation there is one section about the sizing of the pool, 
which I like to discuss:

"If you really want to use shared pooling (why?), then set the max count 
to the same as the number of threads to ensure threads don't wait on 
each other."

First: I think pooling is a valid option even for user-centric 
scenarios. Think about simulating the sql requests of an application 
server. In such a case a pool would have been used, so why not when 
simulating it?

So for this part, I question the part "...(why?)..." and the "really" in 
front of it.

Second: When a pool is used (at least the dbcp2 pool) the connections 
seem to be stored in a stack like construct. So in a uncontended load 
situation the pool will use only a fraction of the configured size and 
in a contended situation with really many threads it will probably 
overload the db.

So all in all I would rather change the sentence to something like "If 
you want to use shared pooling, then set the max count to something 
sensible".

Regards,
 Felix