> i discover that when i setup the page buffer on the isc_attach_database (with isc_dpb_num_buffers) then the parameter is used ONLY
> IF the database page buffer was explicity set to 0 at the database level !
>
> but if i set a page buffer on the connection (for exemple because i will do intensive update), it's mean i want this page buffer
> in any case, even if in the database it's was set to a lower value (that i imagine fit the normal usage of the database)

Yes, number of pages set by database administrator has higher precedence
than arbitrary value set during connect, otherwise irresponsible users could
easily cause fb server to run out of virtual space.

In classic server you should be able to increase number of buffer pages
for single connection only.

But playing with cache size will not solve your speed problems anyway.