server config, <VirtualHost>, <Global>
mod_ldap v1.1 - 2.8.23
LDAPNegativeCache specifies whether or not to cache negative responses from the LDAP server when using LDAP for UID/GID lookups. This option is useful if you also use/are in transition from another authentication system; if there are many users in your old authentication system that aren't in the LDAP database, there can be a significant delay when a directory listing is performed as the UIDs not in the LDAP database are repeatedly looked up in an attempt to present usernames instead of UIDs in directory listings. With LDAPNegativeCache set to on, negative ("not found") responses from the LDAP server will be cached and speed will improve on directory listings that contain many users not present in the LDAP database.