1.postgres 开启wal归档：
a.修改wal_level参数：
alter system set wal_level= ‘replica’;
postgres=# alter system set wal_level= ‘replica’;
ALTER SYSTEM
b.修改archive_mode参数：
alter system set archive_mode= ‘on’;
postgres=# alter system set archive_mode= ‘on’;
ALTER SYSTEM
c.修改archive_command 参数：
alter system set archive_command = ‘/bin/cp -i %p /pgdata/10/archive_wal/%f’;
postgres=# alter system set archive_command = ‘/bin/cp -i %p /pgdata/10/archive_wal/%f’;
ALTER SYSTEM
2.PostgreSQL手动切换WAL日志的命令：
PG10之前：
select pg_switch_xlog();
PG10之后：
select pg_switch_wal();
