[Fedora-directory-users] Use of SLAPI_PLUGIN_BE_POST_MODIFY_FN

I would like to perform an action if and only if a database operation succeeds, as well as revert that database operation if the action fails. From the documentation I understand I should wrap both in a transaction and implement it through these parameters: SLAPI_PLUGIN_BE_POST_MODIFY_FN, SLAPI_PLUGIN_BE_POST_ADD_FN, SLAPI_PLUGIN_BE_POST_DELETE_FN. However I'm not sure how to write that transaction. Is there a code sample? How should I configure the plugin -- nsslapd-plugintype: postperation doesn't seem to be the right type...