DG 增量恢复

如果DG备库缺少大量归档日志，而且主库对应的归档已经被删除，这时候则需要做增量恢复。

具体步骤如下：

1 关闭备库同步

alter database recover managed standby database cancel;

2 以备库的当前SCN号为起点，在主库上做一个增量备份

--备库查询当前 scn 号：
sqlplus / as sysdba
select to_char(current_scn) from v$database;
select to_char(min(checkpoint_change#)) from v$datafile_header;


--确认主备GAP期间是否新增数据文件：
sqlplus / as sysdba
select file# , NAME from v$datafile where creation_change# > = 2212269838;
FILE# NAME
---------- --------------------------------------------------
25 /oracle/XXX/oradata/XXX.data15


注意： 如果存在新增数据文件，备库恢复时需要先restore新添加的数据文件。没有则忽略。


--主库根据备库scn号进行增量备份：
rman target /
run{
allocate channel c1 type disk;
allocate channel c2 type disk;
crosscheck archivelog all;
delete expired archivelog all;
backup current controlfile for standby reuse format '/data/20230303gapincre/standby.ctl';
backup datafile 25 format '/data/20230303gapincre/ForStandby_%U' tag 'FORSTANDBY';
backup INCREMENTAL from scn 2212269837 database format '/data/20230303gapincre/incre_%U';
release channel c1;
release channel c2;
}

查看进度：

col opname format a32
col target_desc format a32
col perwork format a12
set lines 131
select sid,OPNAME,TARGET_DESC,sofar,TOTALWORK,trunc(sofar/totalwork*100,2)||'%' as perwork
from v$session_longops where sofar!=totalwork and totalwork!=0;

3 将增量备份和控制文件拷贝到备库上

主库拷贝增量备份和控制文件至备库：
scp -r /tmp/bak 192.168.202.134:/home/oracle

注意： 确认备库的磁盘空间是否足够存放。

4 使用新的控制文件将备库启动到mount状态

--备库关闭数据库实例，开启至nomount状态：
sqlplus / as sysdba
shutdown immediate
startup nomount


--备库恢复新的控制文件,开启到mount状态：
rman target /
restore standby controlfile from '/oradata/20230302gapincre/standby.ctl';
sql 'alter database mount';

5 增量备份注册到RMAN的catalog恢复增量备份

--restore新添加的数据文件,并catalog注册数据文件到控制文件，由于主备的数据文件目录不一致，需要使用switch命令修改controlfile中数据文件位置：
rman target /
run
{
catalog start with '/oradata/20230303gapincre';
set newname for datafile 25 to '/......';        --如果备库配置了datafile covert参数，这步可忽略
restore datafile 25;
switch datafile all;
}

RMAN> report schema;--查看数据库目录结构，可以查看那些datafile需要switch


--备库开启恢复增量备份：
recover database noredo;
run {
allocate channel c1 type disk;
allocate channel c2 type disk;
allocate channel c3 type disk;
allocate channel c4 type disk;
recover database noredo;
release channel c1;
release channel c2;
release channel c3;
release channel c4;
}

6 清空standby redo log

select 'ALTER DATABASE CLEAR LOGFILE GROUP '|| GROUP# ||';' from v$logfile where TYPE='STANDBY' group by GROUP#;

7 开启备库的恢复进程

--备库开启日志同步进程：
sqlplus / as sysdba
alter database open read only;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT FROM SESSION;

--主库重新激活同步：
sqlplus / as sysdba
ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_2=defer;
ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_2=enable;

--查询是否存在GAP，确认主备是否同步：
sqlplus / as sysdba
SELECT * FROM V$ARCHIVE_GAP;
SELECT max(sequence#) from v$archived_log where applied='YES';
SELECT PROCESS, STATUS, THREAD#, SEQUENCE#, BLOCK#, BLOCKS FROM V$MANAGED_STANDBY; --多刷新几次

--测试：
insert into t1 values(2);
commit;


--备份进度
SELECT sid,
serial#,
CONTEXT,
sofar,
totalwork,
round(sofar / totalwork * 100,
2) "%_COMPLETE"
FROM gv$session_longops
WHERE opname LIKE 'RMAN%'
AND opname NOT LIKE '%aggregate%'
AND totalwork != 0
AND sofar <> totalwork;

--恢复进度
SELECT sid,
serial#,
CONTEXT,
sofar,
totalwork,
round(sofar / totalwork * 100,
2) "% Complete"
FROM v$session_longops
WHERE opname LIKE 'RMAN:%'
AND opname NOT LIKE 'RMAN: aggregate%';