HELP: Lost connection to MySQL server during query

Hello. I'm testing MySQL with a simple script (written in php language)
that executes 50 "insert" and 1 "delete".
When I run this script, it works.
When I run 20 simultaneous copies of the same script, on 20 different
databases, they work.
When I run 25 simultaneous copies of it, on 25 different databases, they
don't work and I obtain this error:
Error 2013: Lost connection to MySQL server during query
on the delete query of each script.
Even if I try to access a database while the scripts are running, mysql
client wait for some time and then it writes the error 2013.

My goal is to make things work with 100 databases.

I suppose something is wrong in configuration files.
Thank you very much for any suggestion,
Alessandro.

Alessandro Topo Galileo ha scritto:

> When I run 25 simultaneous copies of it, on 25 different databases, they
> don't work and I obtain this error:
> Error 2013: Lost connection to MySQL server during query

I have increased innodb_buffer_pool_size to 512M and now this problem
seems to be solved, but when I launch 75 scripts (on 75 different
databases) at the same time, some of them (4 or 5) fail to connect.
Any suggestion?