I've used Kodo in the past for persistence and it's second level cache increased performance significantly. I'm now considering moving to Hibernate and have been looking at the documentation at the Hibernate second level cache and a have found the wording puzzling in section 6.2.1 (Version 4 docs):

"By default, entities are not part of the second-level cache, and their use is not recommended. If you absolutely must use entities, set the shared-cache-mode element in persistence.xml, or use property javax.persistence.sharedCache.mode in your configuration."

Looking at older versions of documentation from 3.x, I don't see this kind of statement that recommends against using entities in the second level cache. I would have presumed that having entities in the second level cache is how you'd get good performance from it. Anyone know why its use is now not recommended? I was thinking of using ehcache for the second level cache which seemed to have been the default provider from old articles I've read.

Hi hjo,




I think this sentence is expressed unhappily.
What's this sentence intends to say in my opinion is:

It it not recommended to set entity caching javax.persistence.sharedCache.mode to ALL or to DISABLE_SELECTIVE
You should indeed use caching javax.persistence.sharedCache.ENABLE_SELECTIVE (=default)
and explicitly mark determinate entity classes as cachable. This is the default and recommended value.

There's also the note:


I guess the motivations are:
-enabling sharedCache.mode to ALL may cause the 2L-Cache requiring to much ressources (or the 2L-Cache becomes rather ineffective due to many evictions and re-puts)
-with selective enabling you can use concurrency strategies which are more appropriate for the given classes.
For example is the content of a entity class is static, you should use the read-only concurrency strategy for it.

I use Hibernate since more than a year sucessfully with 2L-cache caching entities as well as collections and queries.
So far I never encountered problems and the performance gain was clearly measureable.

Thanks - appreciate the useful info you've provided!

Second level cache is always good choice...!!!!

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