Add docs for Iceberg delete_orphan_files

docs/src/main/sphinx/connector/iceberg.rst

@@ -215,8 +215,27 @@ The procedure affects all snapshots that are older than the time period configur
 
   ALTER TABLE test_table EXECUTE expire_snapshots(retention_threshold => '7d')
 
-The ``iceberg.expire_snapshots.min-retention`` catalog configuration property prevents from running
-``expire_snapshots`` with ``retention_threshold`` set to value lower than ``iceberg.expire_snapshots.min-retention``.
+The value for ``retention_threshold`` must be higher than ``iceberg.expire_snapshots.min-retention`` in the catalog
+otherwise the procedure will fail with similar message:
+``Retention specified (1.00d) is shorter than the minimum retention configured in the system (7.00d)``.
+The default value for this property is ``7d``.
+
+delete_orphan_files
+~~~~~~~~~~~~~~~~~~~
+
+The ``delete_orphan_files`` command removes all files from table's data directory which are
+not linked from metadata files and that are older than the value of ``retention_threshold`` parameter.
+Deleting orphan files from time to time is recommended to keep size of table's data directory under control.
+
+``delete_orphan_files`` can be run as follows:
+
+.. code-block:: sql
+
+  ALTER TABLE test_table EXECUTE delete_orphan_files(retention_threshold => '7d')
+
+The value for ``retention_threshold`` must be higher than ``iceberg.delete_orphan_files.min-retention`` in the catalog
+otherwise the procedure will fail with similar message:
+``Retention specified (1.00d) is shorter than the minimum retention configured in the system (7.00d)``.
 The default value for this property is ``7d``.
 
 .. _iceberg-type-mapping: