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diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
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index 3a84321..19e3e36
*** a/doc/src/sgml/config.sgml
--- b/doc/src/sgml/config.sgml
*************** SET ENABLE_SEQSCAN TO OFF;
*** 2590,2595 ****
--- 2590,2597 ----
<para>
Sets the planner's estimate of the cost of a
non-sequentially-fetched disk page. The default is 4.0.
+ (The default is lower than the typical difference between random
+ and sequential storage access speed because of caching effects.)
This value can be overridden for tables and indexes in a particular
tablespace by setting the tablespace parameter of the same name
(see <xref linkend="sql-altertablespace">).