通過歸檔日志定期增量同步數據實驗：
一、再次實驗從歸檔持續同步的方式：
1.修改主庫，開啟歸檔，將日志歸檔到從庫：
archive_mode = on
archive_command = 'ssh 192.168.5.133 test ! -f /home/kingbase/test_fy/archive/%f && scp %p 192.168.5.133:/home/kingbase/test_fy/archive/%f'
wal_keep_segments = 1024
max_wal_senders = 8
2.備庫需要從主庫拉取全量備份：
pg_basebackup -D ./data -R -h 192.168.5.132 -p 54328 -U SYSTEM -w
3.備庫recovery.conf文件：
restore_command = 'cp /home/kingbase/test_fy/archive/%f %p'
standby_mode = on
這種方法是同步的，當備庫需要的日志沒有時，會一直提示：
LOG: restored log file "00000001000000000000004E" from archive
cp: cannot stat `/home/kingbase/test_fy/archive/00000001000000000000004F': No such file or directory
cp: cannot stat `/home/kingbase/test_fy/archive/00000001000000000000004F': No such file or directory
cp: cannot stat `/home/kingbase/test_fy/archive/00000001000000000000004F': No such file or directory
cp: cannot stat `/home/kingbase/test_fy/archive/00000001000000000000004F': No such file or directory
二、在一的基礎上，定期拷貝wal文件
1.關閉歸檔，並重啟數據庫：
2.產生新的數據，並拷貝到從庫歸檔路徑：
scp /home/kingbase/test_fy/data/sys_xlog/* 192.168.5.133:/home/kingbase/test_fy/archive/
3.從庫數據庫會從歸檔目錄中獲取到增量的日志並回放
cp: cannot stat `/home/kingbase/test_fy/archive/000000010000000000000050': No such file or directory
cp: cannot stat `/home/kingbase/test_fy/archive/000000010000000000000050': No such file or directory
cp: cannot stat `/home/kingbase/test_fy/archive/000000010000000000000050': No such file or directory
cp: cannot stat `/home/kingbase/test_fy/archive/000000010000000000000050': No such file or directory
cp: cannot stat `/home/kingbase/test_fy/archive/000000010000000000000050': No such file or directory
LOG: restored log file "000000010000000000000050" from archive
LOG: restored log file "000000010000000000000051" from archive
LOG: restored log file "000000010000000000000052" from archive
三、結論：
通過日志文件拷貝的方式，可以實現增量數據的交換和同步
備注：
1）wal日志拷貝可以從主庫歸檔目錄中獲取。
2）拷貝完成的wal日志，可以從歸檔中刪除。例如，寫一個腳本，同步前一天的數據，並刪除。
3）備庫始終是只讀的。