+.TP
+.B upper_needs_cast { yes | no }
+Set this directive to
+.B yes
+if
+.B upper_func
+needs an explicit cast when applied to literal strings. The form
+.B cast (<arg> as varchar(<max DN length>))
+is used, where
+.B <max DN length>
+is builtin.
+This is
+.B experimental
+and may change in future releases.
+.TP
+.B concat_pattern <pattern>
+This statement defines the
+.B pattern
+to be used to concatenate strings. The
+.B pattern
+MUST contain two question marks, '?', that will be replaced
+by the two strings that must be concatenated. The default value is
+.BR "CONCAT(?,?)";
+a form that is known to be highly portable is
+.BR "?||?",
+but an explicit cast may be required when operating on literal strings:
+.BR "cast(?||? as varchar(<length>))".
+On some RDBMSes the form
+.B "?+?"
+is known to work.
+Carefully check the documentation of your RDBMS or stay with the examples
+for supported ones.
+This is
+.B experimental
+and may change in future releases.
+.TP
+.B strcast_func <SQL function name>
+Specifies the name of a function that converts a given value to a string
+for appropriate ordering. This is used in "SELECT DISTINCT" statements
+for strongly typed RDBMSes with little implicit casting (like PostgreSQL),
+when a literal string is specified.
+This is
+.B experimental
+and may change in future releases.
+.TP
+.B has_ldapinfo_dn_ru { yes | no }
+Explicitly inform the backend whether the SQL schema has dn_ru column
+(dn in reverse uppercased form) or not.
+Overrides automatic check (required by PostgreSQL/unixODBC).
+This is
+.B experimental
+and may change in future releases.
+
+.TP
+.B fail_if_no_mapping { yes | no }
+When set to
+.B yes
+it forces write operations to fail if no appropriate mapping between LDAP
+attributes and SQL data is available. The default behavior is to ignore
+those changes that cannot be mapped correctly.
+This is
+.B experimental
+and may change in future releases.