The document you referenced is for a completely different product.
Since we do not do LDAP synchronizations in version 9.0 and higher, we will now cache the responses we get from your LDAP server. There is a button on the Directory Integration section under Administration labeled Preload Cache which wiil perform a task similar to an LDAP Sync.
You never said why you want to do this, but keep in mind that this cache will expire, so you will need to keep the connection between SMG and Domino on port 389 open.