e29e9469_IBM_WebSphere_Portal_7_anage_the_federated_repository_Description
[Task] Property extension database; formerly known as the lookaside database [Description] 
Choose this option to store additional attributes inside the VMM property extension instead of within the LDAP user registry. Some applications, such as Common Mail portlet and IBM Lotus Web Content Management use the property extension database to store additional attributes. After you enable the property extension database, you can add attributes to meet your business needs.
IBM®WebSphere Portal 7