Specifies the maximum number of aliases to dereference when trying to
resolve an entry, used to avoid infinite alias loops. The default is 1.
.TP
+.B overlay <overlay-name>
+Add the specified overlay to this database. An overlay is a piece of
+code that intercepts database operations in order to extend or change
+them. Overlays are pushed onto
+a stack over the database, and so they will execute in the reverse
+of the order in which they were configured and the database itself
+will receive control last of all.
+.TP
.B readonly on | off
This option puts the database into "read-only" mode. Any attempts to
modify the database will return an "unwilling to perform" error. By