Add a paragraph explaining what restartpoints are. Mention that

wal_keep_segments does not take effect during recovery.

Fujii Masao

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 2fbe6a8c24b460d6a07944ef8dcc80765091a7bf..24307458d8f2b05707dfc2a9b0f4d18e53a5b336 100644 (file)
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1,4 +1,4 @@
-
+
 
 
   Server Configuration
@@ -1926,7 +1926,8 @@ SET ENABLE_SEQSCAN TO OFF;
         doesn't keep any extra segments for standby purposes, and the number
         of old WAL segments available to standby servers is a function of
         the location of the previous checkpoint and status of WAL
-        archiving.  This parameter can only be set in the
+        archiving.  This parameter has no effect on restartpoints.
+        This parameter can only be set in the
         postgresql.conf file or on the server command line.
        
        

diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 0c83032968a0568e22cab230dc3d344385dfbd2c..12bf154c31f3147d795b375ee8bcf2c5cbe359db 100644 (file)
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -1,4 +1,4 @@
-
+
 
 
  Reliability and the Write-Ahead Log
@@ -449,6 +449,7 @@
   
    There will always be at least one WAL segment file, and will normally
    not be more than (2 + checkpoint_completion_target) * checkpoint_segments + 1
+   or checkpoint_segments +  + 1
    files.  Each segment file is normally 16 MB (though this size can be
    altered when building the server).  You can use this to estimate space
    requirements for WAL.
@@ -460,6 +461,22 @@
    of recycled until the system gets back under this limit.
   
 
+  
+   In archive recovery or standby mode, the server periodically performs
+   restartpointsrestartpoint
+   which are similar to checkpoints in normal operation: the server forces
+   all its state to disk, updates the pg_control file to
+   indicate that the already-processed WAL data need not be scanned again,
+   and then recycles any old log segment files in pg_xlog
+   directory. A restartpoint is triggered if at least one checkpoint record
+   has been replayed and checkpoint_timeout seconds have passed
+   since last restartpoint. In standby mode, a restartpoint is also triggered
+   if checkoint_segments log segments have been replayed since
+   last restartpoint and at least one checkpoint record has been replayed.
+   Restartpoints can't be performed more frequently than checkpoints in the
+   master because restartpoints can only be performed at checkpoint records.
+  
+
   
    There are two commonly used internal WAL functions:
    LogInsert and LogFlush.