实战经验：Oracle DG 的归档缺失修复

客户某天反馈说：”DG库自0221以来就已经不同步了，请核查。“

于是我远程登录进行查看。

故障检查

检查归档同步情况

一、查看数据库的情

select database_role,flashback_on,open_mode,current_scn from v$database
DATABASE_ROLE FLASHBACK_ON OPEN_MODE CURRENT_SCN---------------- ------------------ -------------------- ---------------PHYSICAL STANDBY NO        READ ONLY WITH APPLY  16657544972059

二、查看归档的最大线程与最大接收的归档情况。

select thread#,max(sequence#) from v$archived_log group by thread#;
生产库：SQL> select thread#,max(sequence#) from v$archived_log group by thread#; THREAD# MAX(SEQUENCE#)---------- -------------- 1 136973 2 132693 4 149599 3 133277--DG库SYS@hisnewdb> select thread#,max(sequence#) from v$archived_log group by thread#;
 THREAD# MAX(SEQUENCE#)---------- -------------- 1 136973 2 132693 4 149598 3 133277

  • 可见4个节点归档是都有会过来的，sequence都能对得上。

三、查是否存在GAP

select * from v$archived_gap;

日志应用情况

查看延时的应用情况

select name ,value,time_computed from v$dataguard_stats where rownum<33;
NAME VALUE TIME_COMPUTED-------------------------------- ---------------------------------------------------------------- ------------------------------transport lag +11 06:41:27 03/04/2021 16:41:20apply lag +11 06:41:27 03/04/2021 16:41:20apply finish time +00 04:23:39.868 03/04/2021 16:41:20estimated startup time 37 03/04/2021 16:41:20

  • 可看到apply lag的应用已经延时11天6小时了。

  • apply finish time应用最快的恢复时长为4小时。

恢复思路

应用日志

alter database recover managed standby databse cancel; --取消应用日志alter database open read only; --打开只读库alter database recover managed standby ; alter database recover managed standby disconnect from session; -- 后台应用，建议上面命令，放前台应用。

归档还保留或者GAP较少的情况

1）归档还在主库

方法一：

  1. 首先通过备库sql查出相应的 node[thread#] 和归档位置 name：

    select name from v$archived_log where sequence# between &1 and &2 and thread# = &3;

  2. 传输上面文件到备库归档位置 archive log list

    #1.asmcd命令 本地环境与asm存储cp自由。cp arch*.pdf /home/oracle/1.dbf

  3. 备库上注册归档文件alter database register logfile '归档文件绝对路径' 或rman注册日志catalog start with '';

  4. 应用日志，查看select * from V$ARCHIVE_GAP;,监视是否还存在其它的GAP出现。如出现，如上面步骤循环操作。

方法二：

  1. 在配置 fal_client=${备库的监听} 和 fal_server=${主库的监听}

  2. 直接应用日志，由备库寻找日志。

2）归档已在备库

应用日志

归档已经被删除或GAP较多的情况

查看归档所在的位置

alert.log日志：

  • 提供等thread 线程4的序列为148164的归档，获取的序号有148164-148165

  • control_keep_record_keep_time是控制文件的重用记录数据。提示在这个记录天数内没找到归档文件，建议设置更长些天数。以便GAP找到缺失的日志。

    • 默认7天，1-365天范围。

    • 记录的是归档日志，各种备份记录。

    • 不记录数据文件，表空间，redo thread记录。除非被drop，否则不会重用这部分记录

started logmerger processThu Mar 04 16:19:53 2021Managed Standby Recovery not using Real Time ApplyParallel Media Recovery started with 16 slavesWaiting for all non-current ORLs to be archived...All non-current ORLs have been archived.Media Recovery Waiting for thread 4 sequence 148164Fetching gap sequence in thread 4, gap sequence 148164-148165Thu Mar 04 16:19:57 2021Completed: alter database recover managed standby database disconnect from session----------Thu Mar 04 16:21:50 2021FAL[client]: Failed to request gap sequence GAP - thread 4 sequence 148164-148165 DBID 3828421454 branch 984679630FAL[client]: All defined FAL servers have been attempted.------------------------------------------------------------Check that the CONTROL_FILE_RECORD_KEEP_TIME initializationparameter is defined to a value that's sufficiently largeenough to maintain adequate log switch information to resolvearchivelog gaps.------------------------------------------------------------ Thu Mar 04 16:22:25 2021RFS[18]: Selected log 29 for thread 4 sequence 149600 dbid -466545842 branch 984679630Thu Mar 04 16:22:25 2021

1）找到当前的最小SCN

对比数据文件最后检查点的scn，数据文件头部检查点的scn，缺失归档的对应scn（下个日志文件第一个更改号），当前数据库的scn：

select thread#,low_sequence#,high_sequence# from v$archive_gap; col datafile_scn for 999999999999999col DATAFILE_HEADER_SCN for 999999999999999col current_scn for 999999999999999col next_change# for 999999999999999select ( select min(d.checkpoint_change#) from v$datafile d ) datafile_scn , ( select min(d.checkpoint_change#) from v$datafile_header d where rownum=1) datafile_header_scn, (select current_scn from v$database) current_scn, (select next_change# from v$archived_log where sequence#=148164 and resetlogs_change# = (select d.resetlogs_change# from v$database d ) and rownum=1 ) next_change#from dual;
DATAFILE_SCN DATAFILE_HEADER_SCN CURRENT_SCN NEXT_CHANGE#---------------- ------------------- ---------------- ---------------- 16657544969028 16657544972060 16657544972059

  • 取上面最小的scn作为增量备份的SCN

2）主库做SCN增量备份

停用备库的日志应用

alter database recover managed standby database cancel;

rman备份

  1. 切换日志

  2. 切记备份当前控制文件

  3. 增量scn备份

run {allocate channel c1 device type disk; allocate channel c2 device type disk; allocate channel c3 device type disk; allocate channel c4 device type disk; allocate channel c5 device type disk; allocate channel c6 device type disk; CONFIGURE DEVICE TYPE DISK PARALLELISM 6 BACKUP TYPE TO BACKUPSET;backup as compressed backupset current controlfile for standby format '/home/oracle/backup/backup_ctl_%U.rman';backup as compressed backupset incremental from scn 16657544969028 database format '/home/oracle/backup/backup_%d_%s_%c_%U_%T.rman' include current controlfile for standby filesperset 10 tag 'forsdb_16657544969028_0304';release channel c1 ; release channel c2 ; release channel c3 ; release channel c4 ; release channel c5 ; release  channel c6 ; 

传输备份文件到备库

scp -rp /home/oracle/backup/backup host2:/home/oracle

介质恢复备库

  1. 查出控制文件的绝对目录位置，后停备库

  2. 启动到nomount

  3. 恢复控制文件

  4. 启动到mount

  5. 恢复数据文件

  6. 检查rman进展

select name from v$controlfile;shu immediate;startup nomount;
rman target / <<eofrestore standby controlfile from '/home/oracle/backup/backup_ctl_%U.rman';alter database mount; eof

  • 如果没有单独备份standby controlfile，就一个一个文件来测试恢复standby controflie

restore standby controlfile to '/oradata/hisnewdb/control01.ctl' from  '/home/oracle/backup/某个文件';

  • 如果文件太多，可以先rman注册文件后，再恢复控制文件。

    • 要找开备库mount状态才能注册

rmant target / <<eofstartup mount; catalog start with '/home/oracle/backup/';list backup of controlfile;restore standby controlfile automatic;eof#大概是这样。restore standby controlfile automatic;如果不通，就采用上面list的信息，找到具体含有standby controflile的备份文件，再通过restore standby controfile from '';来恢复 。
catalog start with '/home/oracle/backup/';recover database noredo;

查看rman的恢复进展：

set line 9999select sid,serial#,opname,round(sofar/totalwork*100) completed,trunc(elapsed_seconds/60) elapsed ,trunc(time_remaining/60) remaining,context ,target,sofar,totalworkfrom v$session_longopswhere opname like 'RMAN%' and opname not like '%aggregate%' and totalwork!=0 and sofar<>totalwork;

应用日志

检查standby redo files是否存在:

select * from v$standby_log;

注册standby redolog files

-- 添加单个文件：alter database add standby logfile group {组号} 'standby redo logs files 绝对目录文件';-- 添加多个standby redologs filealter database add standby logfile group {组号} ('standby redo logs file 1','logfiles2');

应用日志

alter database recover managed standby database cancel ; startup mount; alter database open read only;select open_mode,status,protection_level,protection_mode from v$database ;--前台应用日志alter database recover managed standby database ; -- 8 parallel 后台应用日志alter database recover managed standby database parallel 8 disconnect from session;

检查应用日志的情况

检查各个线程thread#的最大应用日志的序列，与主库进行对比。

select thread#,max(sequence#) from v$archived_log where applied='YES' group by thread#;

墨天轮原文链接：https://www.modb.pro/db/46707（复制到浏览器或者点击“阅读原文”立即查看）

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