I am using NHibernate.Caches.Prevalence for my second level cache.

When I load the data from DB in the first time, the cache works. The cache saves the data into files on disk.

But it seems that the data it stored would never be expired. :shock:

Envirement:
In dll.config
<add key="hibernate.cache.provider_class" value="NHibernate.Caches.Prevalence.PrevalenceCacheProvider, NHibernate.Caches.Prevalence" />
<add key="relativeExpiration" value="20" />

In hbm.xml:
<cache usage="read-only"></cache>

I use NUnit to run the dll.

"relativeExpiration" is a config setting for SysCache, not PrevalenceCache. Could you post your logs? At the DEBUG level they should show some caching messages.

I think the problem I met is that the cache didn't expire.

Is there an expiration config setting for PrevalenceCache?

No, not at the moment.