[Zope] Knowing the Zope database is configured read-only

Hello, A CMF/CPS site I work on needs to switch to read-only-database mode sometimes, to be only viewed but not edited. The problem is when being in this mode, I would like to hide some actions or links pointing to methods adding or editing content. Is there a simple way to know from code (zpt, script, Condition of actions) that the main database has been set read-only ? Thanks in advance for hints, -- Damien