[Zope] ZODB config question

[Tim Peters]

[Pascal Peregrina]
> I would like to know what is the difference between these 2 ZODB config
> params :
>    <key name="pool-size" datatype="integer" default="7"/>
>    <key name="version-pool-size" datatype="integer" default="3"/>

Before ZODB 3.3.1, there's a hard limit on the number of
simultaneously open DB Connections.  Well, there are two hard limits,
one for DB.open() calls that pass a non-empty string as the value of
the optional version= argument (that limit is version-pool-size), and
the other is for all other DB.open() calls (connections not "in a
version", & that limit is pool-size).

If you don't use versions (which are, as Chris said, deprecated),
version-pool-size has no effect.

If you try to open more Connections than the appropriate limit, the
DB.open() call will block until a Connection of the requested flavor
(version versus non-version) is closed.  Because the _usual_ outcome
in this case is that the call blocks forever, in ZODB 3.3.1 there are
no hard limits here (although these config options still exist, and
exceeding them logs advisory messages).