[Dovecot] Change passwd backend over cron: what happens if changes while reading?

hi,

I want to use two backends für DoveCot. One generated file from the LDAP tree, and the real LDAP.

The first backend is generated from a cronjob thats reads the whole ldap server and converts them into a DoveCot passwd file.

I red in the Wiki, if the user password isn't correct, than DoveCot asks the second backend (LDAP). Is this correct? Because, the the user can change his password, but Cron generates only every hour the file. So the password in the passwd-file isn't correct, until Cron runs again.

The second, what happens, if Dovecot reads the file and in the same moment, Cron generate the new file? Does he change to the second backend? Or do I (the user) get an error?

cu denny