This is a known issue and we have reported to Novell few times over the years but haven’t had any response. We also noticed the process to add entries into Address Book (AB) slow dramatically after 250-300 entries.
You can place debug trace into your applet to see the performance. We will recommend to place debug trace before & after you access database, add entry into AB, after entry added into AB. See the forum post below to use the debug view: