PostgreSQL的xlog实验一

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一，从initdb开始，initdb执行结束后，看xlog:

[pgsql@localhost pg_xlog]$ ls -lrt

total 16408
drwx------ 2 pgsql pgsql     4096 Aug  6 10:41 archive_status
-rw------- 1 pgsql pgsql 16777216 Aug  6 10:41 000000010000000000000001
[pgsql@localhost pg_xlog]$ 

然后，设置参数为这样：

archive_mode = on               # allows archiving to be done
                                # (change requires restart)
...
archive_command = 'copy %p "/home/pgsql/archive_log/%f"'   # command to use to archive a logfile segment
#archive_timeout = 0            # force a logfile segment switch after this
                                # number of seconds; 0 disables

wal_level = archive                     # minimal, archive, or hot_standby
                                        # (change requires restart)

二，启动PostgreSQL，然后一直等待...

看xlog是否有变化，等了一个小时以上，没有发现变化。

[pgsql@localhost pg_xlog]$ ls -lrt
total 16408
drwx------ 2 pgsql pgsql     4096 Aug  6 10:41 archive_status
-rw------- 1 pgsql pgsql 16777216 Aug  6 11:04 000000010000000000000001
[pgsql@localhost pg_xlog]$ 
[pgsql@localhost pg_xlog]$ 
[pgsql@localhost pg_xlog]$ ls ../../archive_log
[pgsql@localhost pg_xlog]$ 

三，关闭PostgreSQL: ./pg_ctl -D ../../DemoDir stop

可以发现，online redo log增加了一个。

[pgsql@localhost ~]$ ls -lrt ./DemoDir/pg_xlog
total 32812
-rw------- 1 pgsql pgsql 16777216 Aug 6 12:48 000000010000000000000001
drwx------ 2 pgsql pgsql 4096 Aug 6 12:48 archive_status
-rw------- 1 pgsql pgsql 16777216 Aug 6 12:48 000000010000000000000002
[pgsql@localhost ~]$ ls -lrt ./archive_log
total 16404
-rw------- 1 pgsql pgsql 16777216 Aug 6 12:48 000000010000000000000001
[pgsql@localhost ~]$

再次开启： ./pg_ctl -D ../../DemoDir start

因为没有什么操作，所以也无变化：

[pgsql@localhost ~]$ ls -lrt ./DemoDir/pg_xlog
total 32812
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:48 000000010000000000000001
drwx------ 2 pgsql pgsql     4096 Aug  6 12:48 archive_status
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:48 000000010000000000000002
[pgsql@localhost ~]$ ls -lrt ./archive_log
total 16404
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:48 000000010000000000000001
[pgsql@localhost ~]$ 

再次关闭：./pg_ctl -D ../../DemoDir stop

[pgsql@localhost ~]$ ls -lrt ./DemoDir/pg_xlog
total 49216
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:48 000000010000000000000004
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:51 000000010000000000000002
drwx------ 2 pgsql pgsql     4096 Aug  6 12:51 archive_status
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:51 000000010000000000000003
[pgsql@localhost ~]$ ls -lrt ./archive_log
total 32808
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:48 000000010000000000000001
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:51 000000010000000000000002
[pgsql@localhost ~]$ 

四，如果与性中，进行切换log:

postgres=# select pg_switch_xlog();
 pg_switch_xlog 
----------------
 0/3000098
(1 row)

postgres=# 

[pgsql@localhost ~]$ ls -lrt ./DemoDir/pg_xlog
total 49216
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:48 000000010000000000000004
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:51 000000010000000000000002
drwx------ 2 pgsql pgsql     4096 Aug  6 12:56 archive_status
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:56 000000010000000000000003
[pgsql@localhost ~]$ ls -lrt ./archive_log
total 49212
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:48 000000010000000000000001
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:51 000000010000000000000002
-rw------- 1 pgsql pgsql 16777216 Aug  6 12:56 000000010000000000000003
[pgsql@localhost ~]$ 

  

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磨砺技术珠矶，践行数据之道，追求卓越价值