[Dovecot] Disabling auth caching just from one passdb

Hello,

I'm using various password databases (one of them is a ldap database, 

which is the used for users connecting with email clients, and the other with pam, using a pam module integrated with our SSO that is used from our webmail). I would like to disable password caching in my pam database (because 'passwords' provided by our SSO are single use tokens, so caching them has no benefit), but not in the ldap.

As far as I know, auth_cache_size is the option to enable caching in 

all databases. But, is there any option I could use to disable it in a specific password database?

-- Angel L. Mateo Martínez Sección de Telemática Área de Tecnologías de la Información y las Comunicaciones Aplicadas (ATICA) http://www.um.es/atica Tfo: 868889150 Fax: 868888337