add PING-PONG doc

diff --git a/doc/rrdcached.pod b/doc/rrdcached.pod
index 2999eb40ee7f84be025ab1556370ff15a4c695d8..1c29c40158ceff96350ae06f0662055f074666ea 100644 (file)
--- a/doc/rrdcached.pod
+++ b/doc/rrdcached.pod
@@ -646,6 +646,13 @@ Example:
  JournalBytes: 190
  JournalRotate: 0
 
+=item B<PING>
+
+PING-PONG, this is very usefull when using connection pool between user client and RRDCACHED.
+
+Example:
+ 0 PONG
+
 =item B<UPDATE> I<filename> I<values> [I<values> ...]
 
 Adds more data to a filename. This is B<the> operation the daemon was designed