[Pascal Peregrina]
I would like to know if, for a Zeo Storage, increasing the <zodb_db></zodb_db> cache-size param value (per connection target number of cached objects) is useful, specially if I already have a high cache-size param value in the <zeoclient></zeoclient> subsection (global Zeo objects target cache size in bytes).
These are two distinct caches. The "ZODB cache" applies to every way of using ZODB, and is an in-memory cache associated with a Connection. The least-recently used objects are booted out at transaction boundaries, trying to reduce the number of objects in the in-memory cache to the number you specified. The ZEO client cache is a second-level, disk-based cache, specific to ZEO. It only sees requests for objects _not_ satisfied by the in-memory Connection cache. Of course it's faster to satisfy a reference from memory than from any disk-based cache. Whether it will help you to boost the number of objects in the in-memory cache depends on many details you haven't revealed (and may not even know). Try it. A downside is that the RAM needed for the in-memory cache will increase, taking away RAM available for other uses. Do too much of that, and you'll start swapping out RAM to disk. The default sizes for the in-memory Connection cache and the ZEO disk-based cache were set years ago, when "typical" RAM and disk sizes were much smaller than they are now. It will probably help to boost both -- up to some point that depends on details of your HW and object reference patterns.