lightdb_archive_dir='/archive'
lightdb_archive_retention_size=100
archive_mode = on
然后lt_ctl reload数据库，archive_mode如果之前为off状态，需要重启数据库，否则只要执行lt_ctl reload即可
lightdb@postgres=# show archive_mode ;
archive_mode
--------------
on
(1 row)
lightdb@postgres=# show lightdb_archive_retention_size ;
lightdb_archive_retention_size
--------------------------------
100
(1 row)
lightdb@postgres=# show lightdb_archive_dir ;
lightdb_archive_dir
---------------------
/archive
(1 row)11111