pg归档日志的开启与关闭

postgres.conf文件的配置对所有数据库起作用：

postgres=# \l

List of databases

Name | Owner | Encoding | Collate | Ctype | Access privileges

-----------+-------------+----------+-------------+-------------+---------------------------------

postgres | postgres9.6 | UTF8 | en_US.UTF-8 | en_US.UTF-8 |

template0 | postgres9.6 | UTF8 | en_US.UTF-8 | en_US.UTF-8 | =c/"postgres9.6" +

| | | | | "postgres9.6"=CTc/"postgres9.6"

template1 | postgres9.6 | UTF8 | en_US.UTF-8 | en_US.UTF-8 | =c/"postgres9.6" +

| | | | | "postgres9.6"=CTc/"postgres9.6"

test | postgres9.6 | UTF8 | en_US.UTF-8 | en_US.UTF-8 |

(4 rows)

postgres=# \c

You are now connected to database "postgres" as user "postgres9.6".

postgres=# show archive_mode;

archive_mode

--------------

on

(1 row)

postgres=# select pg_switch_xlog();

pg_switch_xlog

----------------

0/C000078

(1 row)

test=# \c

You are now connected to database "test" as user "postgres9.6".

test=# select pg_switch_xlog();

pg_switch_xlog

----------------

0/B02A090

(1 row)

[root@db 20170206]# pwd

/home/postgres9.6/arch/20170206

[root@db 20170206]# ls

00000001000000000000000A 00000001000000000000000B 00000001000000000000000C

============================================================================================================================

开启归档模式：

[postgres9.6@db data]$ pwd

/home/postgres9.6/data

[postgres9.6@db data]$ ll postgresql.conf

-rw------- 1 postgres9.6 postgres 22369 Feb 6 13:35 postgresql.conf

vi postgres.conf修改如下：

wal_level = replica # minimal, replica, or logical

archive_mode = on # enables archiving; off, on, or always

# (change requires restart)

archive_command = 'DATE=`date +%Y%m%d`;DIR="/home/postgres9.6/arch/$DATE";(test -d $DIR || mkdir -p $DIR)&& cp %p $DIR/%f' # command to use to archive a logfile segment

其中： %p表示wal日志文件的路径，%f表示wal日志文件名称。

[postgres9.6@db data]$ pg_ctl stop

waiting for server to shut down.... done

server stopped

[postgres9.6@db data]$ pg_ctl start

server starting

[postgres9.6@db data]$ LOG: database system was shut down at 2017-02-06 13:40:26 CST

LOG: MultiXact member wraparound protections are now enabled

LOG: database system is ready to accept connections

LOG: autovacuum launcher started

postgres=# \c

You are now connected to database "postgres" as user "postgres9.6".

postgres=# select pg_switch_xlog();

pg_switch_xlog

----------------

0/F000120

(1 row)

postgres=# select pg_switch_xlog();

pg_switch_xlog

----------------

0/10000078

(1 row)

postgres=# show archive_mode;

archive_mode

--------------

on

(1 row)

test=# \c

You are now connected to database "test" as user "postgres9.6".

test=# select pg_switch_xlog();

pg_switch_xlog

----------------

0/11000078

(1 row)

test=# show archive_mode;

archive_mode

--------------

on

(1 row)

[root@db 20170206]# pwd

/home/postgres9.6/arch/20170206

[root@db 20170206]# ls

00000001000000000000000F 000000010000000000000010 000000010000000000000011

##### pg里不同数据库之间日志（归档日志或者pc_xlog）（目录）是共享的。####

关闭归档模式：

将以上三个参数注释或者修改即可