A directory channel can service multiple pseudo domains. To apply a channel option to only a specific pseudo domain, prefix the option name with the name of the pseudo domain name followed by an underscore, _. See, for instance, the second example option file presented in Section 3.2.6.3 . In that example, the LDAP_SERVERS option applies globally while the options prefixed with "acme.com_" apply only to the acme.com pseudo domain. Likewise, the options prefixed with "sales.acme.com_" apply only to the sales.acme.com pseudo domain.
An option setting prefixed with the pseudo domain name always takes precedence over a global option setting for the associated pseudo domain. For instance, in the option file
SIZELIMIT=20 a1.acme.com_SIZELIMIT=10the pseudo domain a1.acme.com will use the value 10 for the SIZELIMIT option. All other domains will use the value 20 for that same option.