Fix CLogTruncationLock documentation.

nmisch · nmisch · commit 3cbbd3515aa6 · 2019-02-17T00:51:19.000-08:00
Back-patch to v10, which introduced the lock.
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
@@ -1044,7 +1044,8 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
         </row>
         <row>
          <entry><literal>CLogTruncationLock</literal></entry>
-         <entry>Waiting to truncate the write-ahead log or waiting for write-ahead log truncation to finish.</entry>
+         <entry>Waiting to execute <function>txid_status</function> or update
+         the oldest transaction id available to it.</entry>
         </row>
         <row>
          <entry><literal>clog</literal></entry>
