Update documentation for direct_io configuration.

2 files changed, 12 insertions, 3 deletions

diff --git a/dist/api_data.py b/dist/api_data.py
index 2550c405520..412f0603efd 100644
--- a/dist/api_data.py
+++ b/dist/api_data.py
@@ -613,7 +613,12 @@ methods = {
 	    Use \c O_DIRECT to access files.  Options are given as a list,
 	    such as <code>"direct_io=[data]"</code>.  Configuring
 	    \c direct_io requires care, see @ref
-	    tuning_system_buffer_cache_direct_io for important warnings''',
+	    tuning_system_buffer_cache_direct_io for important warnings.
+		Including \c "data" will cause WiredTiger data files to use
+		\c O_DIRECT, including \c "log" will cause WiredTiger log files
+		to use \c O_DIRECT, and including \c "checkpoint" will cause
+		WiredTiger data files opened at a checkpoint (i.e: read only) to
+		use \c O_DIRECT''',
 	    type='list', choices=['checkpoint', 'data', 'log']),
 	Config('extensions', '', r'''
 	    list of shared library extensions to load (using dlopen).
diff --git a/src/include/wiredtiger.in b/src/include/wiredtiger.in
index ec4825afade..6334bca2061 100644
--- a/src/include/wiredtiger.in
+++ b/src/include/wiredtiger.in
@@ -1493,8 +1493,12 @@ struct __wt_connection {
  * @config{direct_io, Use \c O_DIRECT to access files.  Options are given as a
  * list\, such as <code>"direct_io=[data]"</code>. Configuring \c direct_io
  * requires care\, see @ref tuning_system_buffer_cache_direct_io for important
- * warnings., a list\, with values chosen from the following options: \c
- * "checkpoint"\, \c "data"\, \c "log"; default empty.}
+ * warnings.  Including \c "data" will cause WiredTiger data files to use \c
+ * O_DIRECT\, including \c "log" will cause WiredTiger log files to use \c
+ * O_DIRECT\, and including \c "checkpoint" will cause WiredTiger data files
+ * opened at a checkpoint (i.e: read only) to use \c O_DIRECT., a list\, with
+ * values chosen from the following options: \c "checkpoint"\, \c "data"\, \c
+ * "log"; default empty.}
  * @config{error_prefix, prefix string for error messages., a string; default
  * empty.}
  * @config{eviction_dirty_target, continue evicting until the cache has less