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创建逻辑dg

2024-07-02 09:14:37   226人阅读

逻辑备用DG
  今天是2014-04-29，最近一直忙的事情，也没来的急写点东西。今天继续整理dg的相关内容，要说的是逻辑dg的创建过程和注意事项。
什么是逻辑dg呢？物理dg类似于主库的完整副本，是块对块的重做应用。但是对于逻辑dg，是类似采用日志挖掘技术将主库传来的redo数据，进行构造sql进而在备库进行应用。且备库可以正常打开，并能维护其他不是主库传送的需要维护的对象。
  那么就存在一个问题，如果在备库采用rowid获得的数据，有可能和主库的完全不一致。那么当在主库修改数据的时候，我们建议在所修改的对象上，创建非空索引或是主键条件，那么在传送到备库的时候，继而能够应用这些约束，避免数据更新的错误性。但有时候并不是非要说一定要在主库建立对象表的主键或是非空索引，如果没有创建了，那么将会产生大量的无用redo，这就是在所有字段上都进行了日志补充导致。

The physical organization in a logical standby database is different from that of the primary database, even though the logical standby database is created from a backup copy of the primary database. Thus, ROWIDs contained in the redo records generated by the primary database cannot be used to identify the corresponding row in the logical standby database.

Oracle uses primary-key or unique-constraint/index supplemental logging to logically identify a modified row in the logical standby database. When database-wide primary-key and unique-constraint/index supplemental logging is enabled, eachUPDATE statement also writes the column values necessary in the redo log to uniquely identify the modified row in the logical standby database.

  • If a table has a primary key defined, then the primary key is logged along with the modified columns as part of theUPDATE statement to identify the modified row.

  • If there is no primary key, then the shortest nonnull unique-constraint/index is logged along with the modified columns as part of theUPDATE statement to identify the modified row.

  • If there is no primary key and no nonnull unique constraint/index, then all columns of bounded size are logged as part of the UPDATE statement to identify the modified row. All columns are logged except the following: LONG, LOB, LONG RAW, object type, and collections.

  • A function-based index, even though it is declared as unique, cannot be used to uniquely identify a modified row. However, logical standby databases support replication of tables that have function-based indexes defined, as long as modified rows can be uniquely identified.

Oracle recommends that you add a primary key or a nonnull unique index to tables in the primary database, whenever possible, to ensure that SQL Apply can efficiently apply redo data updates to the logical standby database.


那么哪些是sql apply支持的类型和不支持哪些类型呢？查看手册如下：

C.1.1 Supported Datatypes in a Logical Standby Database

Logical standby databases support the following datatypes:

  • BINARY_DOUBLE

  • BINARY_FLOAT

  • BLOB

  • CHAR

  • CLOB and NCLOB

  • DATE

  • INTERVAL YEAR TO MONTH

  • INTERVAL DAY TO SECOND

  • LONG

  • LONG RAW

  • NCHAR

  • NUMBER

  • NVARCHAR2

  • RAW

  • TIMESTAMP

  • TIMESTAMP WITH TIMEZONE

  • TIMESTAMP WITH LOCAL TIMEZONE

  • VARCHAR and VARCHAR2

  • LOBs stored as SecureFiles (requires that the primary database be run at a compatibility of 11.2 or higher.

  • XMLType data for all storage models, assuming the following primary database compatibility requirements:

    • XMLType stored in CLOB format requires primary database to run at a compatibility of 11.1 or higher

    • XMLType stored in object-relational format or as binary XML requires that the primary database be running Oracle Database 11g Release 2 (11.2.0.3) or higher with a redo compatibility setting of 11.2.0.3 or higher

C.1.1.1 Compatibility Requirements

SQL Apply support for the following has compatibility requirements on the primary database:

  • Multibyte CLOB support requires primary database to run at a compatibility of 10.1 or higher.

  • IOT support without LOBs and Overflows requires primary database to run at a compatibility of 10.1 or higher.

  • IOT support with LOB and Overflow requires primary database to run at a compatibility of 10.2 or higher.

  • TDE support requires primary database to run at a compatibility of 11.1 or higher.

  • Segment compression requires primary database to run at a compatibility of 11.1 or higher.

  • Hybrid Columnar Compression support is dependent on the underlying storage system.

  通过视图查看主库中的哪些表不能被sql apply ：

[oracle@dg-one ~]$ sqlplus  / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Tue Apr 29 21:30:01 2014

Copyright (c) 1982, 2013, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> 
SQL> desc dba_logstdby_unsupported
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 OWNER                                              VARCHAR2(30)
 TABLE_NAME                                         VARCHAR2(30)
 COLUMN_NAME                                        VARCHAR2(30)
 ATTRIBUTES                                         VARCHAR2(39)
 DATA_TYPE                                          VARCHAR2(32)

SQL> select owner,table_name,column_name,attributes,data_type from dba_logstdby_unsupported;

no rows selected
查看存在唯一性问题的表，如下：
SQL> select * from dba_logstdby_not_unique;

OWNER                          TABLE_NAME                     B
------------------------------ ------------------------------ -
SCOTT                          BONUS                          N
SCOTT                          SALGRADE                       N
STDBYPERF                      STATS$MANAGED_STANDBY          N
STDBYPERF                      STATS$RECOVERY_PROGRESS        N

SQL> desc dba_logstdby_not_unique
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 OWNER                                              VARCHAR2(30)
 TABLE_NAME                                         VARCHAR2(30)
 BAD_COLUMN                                         VARCHAR2(1)

好了，现在开始创建逻辑dg，因为我已经创建了物理 dg，那么我们从该基础上转换成逻辑dg（注：不能从逻辑dg转为物理dg）。如果没有创建物理dg，那么可以
直接去创建逻辑dg，但是注意参数的修改。
第一步：停止备库redo应用：
查看数据库模式：

SQL> set linesize 200                                                                       
SQL> col dest_name for a50
SQL> select database_mode,recovery_mode,protection_mode,dest_name from v$archive_dest_status where database_mode!=‘UNKNOWN‘;

DATABASE_MODE   RECOVERY_MODE           PROTECTION_MODE      DEST_NAME
--------------- ----------------------- -------------------- --------------------------------------------------
OPEN_READ-ONLY  MANAGED REAL TIME APPLY MAXIMUM PERFORMANCE  LOG_ARCHIVE_DEST_1

SQL>

停止redo应用：

SQL> alter database recover managed standby database cancel;

Database altered.

SQL> 
 

第二步：在主库build逻辑dg所需元数据。

SQL> exec dbms_logstdby.build;

PL/SQL procedure successfully completed.

SQL>

注：这个过程主要是做了什么操作呢？

A LogMiner dictionary must be built into the redo data so that the LogMiner component of SQL Apply can properly interpret changes it sees in the redo. As part of building the LogMiner dictionary, supplemental logging is automatically set up to log primary key and unique-constraint/index columns. The supplemental logging information ensures each update contains enough information to logically identify each row that is modified by the statement.

To build the LogMiner dictionary, issue the following statement:

SQL> EXECUTE DBMS_LOGSTDBY.BUILD;

The DBMS_LOGSTDBY.BUILD procedure waits for all existing transactions to complete. Long-running transactions executed on the primary database will affect the timeliness of this command.

Note:

In databases created using Oracle Database 11g release 2 (11.2) or later, supplemental logging information is automatically propagated to any existing physical standby databases. However, for databases in earlier releases, or if the database was created using an earlier release and then upgraded to 11.2, you must check whether supplemental logging is enabled at the physical standby(s) if it is also enabled at the primary database. If it is not enabled at the physical standby(s), then before performing a switchover or failover, you must enable supplemental logging on all existing physical standby databases. To do so, issue the following SQL command on each physical standby:
SQL>  ALTER DATABASE ADD SUPPLEMENTAL LOG DATA (PRIMARY KEY, UNIQUE INDEX) COLUMNS;

If you do not do this, then any logical standby that is also in the same Data Guard configuration will be unusable if a switchover or failover is performed to one of the physical standby databases. If a switchover or failover has already occurred and supplemental logging was not enabled, then you must recreate all logical standby databases

第三步：在备库告诉mrp继续应用redo，达到字典构建时的scn；

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.

Total System Global Area  313159680 bytes
Fixed Size                  2252824 bytes
Variable Size             171970536 bytes
Database Buffers          134217728 bytes
Redo Buffers                4718592 bytes
Database mounted.

SQL> alter database recover to logical standby Amy;

Database altered.

这时我们修改几个地方，首先是db_name;

SQL> alter system set db_name=Amy scope=spfile;

System altered.

SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options


另外还有log_archive_dest_n 参数配置：

SQL> show parameter log_archive_dest_1

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
log_archive_dest_1                   string      location=USE_DB_RECOVERY_FILE_
                                                 DEST valid_for=(all_logfiles,a
                                                 ll_roles)
log_archive_dest_10                  string
log_archive_dest_11                  string
log_archive_dest_12                  string
log_archive_dest_13                  string
log_archive_dest_14                  string
log_archive_dest_15                  string
log_archive_dest_16                  string
log_archive_dest_17                  string

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
log_archive_dest_18                  string
log_archive_dest_19                  string
SQL> show parameter log_archive_dest_2

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
log_archive_dest_2                   string      service=dg1 lgwr sync valid_fo
                                                 r=(online_logfiles,primary_rol
                                                 e) db_unique_name=dg1
log_archive_dest_20                  string


这里需要说明第一个log_archive_dest_1 为什么是all_logfiles呢？因为我们是创建的逻辑备库，逻辑备库除了维护主库的对象外，还可以自己进行其他对象的修改操作那么这些对象的redo，是需要归档的，逻辑备库是一个真实数据库啊，另外如果不指定快速闪回区，那么应该在加一个log_archive_dest_3,将日志分开，另外如果是快速闪回区，可以省略valid_for,因为默认就是all_logfiles,all_roles。
另外要注意：如果逻辑备库和主库在一个相同的数据存储管理上，那么需要使用dbms_logstdby.skip去跳过alter tablespace dml的操作，不然可能产生误修改主库的表空间问题。
第四步：完成逻辑dg的创建：

SQL> shutdown immediat;
SP2-0717: illegal SHUTDOWN option
SQL> shutdown immediate;
ORA-01507: database not mounted


ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.

Total System Global Area  313159680 bytes
Fixed Size                  2252824 bytes
Variable Size             171970536 bytes
Database Buffers          134217728 bytes
Redo Buffers                4718592 bytes
Database mounted.
SQL> alter database open resetlogs;

Database altered.

SQL> alter database start logical standby apply immediate;

Database altered.

SQL> 
SQL> set linesize 200

SQL> select * from v$log

    GROUP#    THREAD#  SEQUENCE#      BYTES  BLOCKSIZE    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM NEXT_CHANGE# NEXT_TIME
---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- --------- ------------ ---------
         1          1          1   52428800        512          1 NO  CURRENT                1335271 29-APR-14   2.8147E+14
         2          1          0   52428800        512          1 YES UNUSED                       0                      0
         3          1          0   52428800        512          1 YES UNUSED                       0                      0

注：resetlogs做什么的？
resetlogs打开讲会对没有归档的redo日志文件中的内容进行覆盖，sequence重新从1开始计算，相当于数据库进入了一个新的化身或是新的生命周期，进入incarnation的目的就是为了不在去应用resetlog之后的日志的lcr。经常有朋友问我resetlog打开数据库了是否就是一个不完全恢复呢？这是一个非常错误的观点，完全恢复和不完全恢复不是依据resetlog定的。而是我们在前滚的时候是否全部应用了日志。如果全部应用了，那么就是一次完全恢复过程。
我们可以查看数据库的原型列表如下；

[oracle@dg-two dbs]$ rman target /

Recovery Manager: Release 11.2.0.4.0 - Production on Tue Apr 29 22:20:46 2014

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

connected to target database: AMY (DBID=1205246033)

RMAN> list incarnation
2> ;

using target database control file instead of recovery catalog

List of Database Incarnations
DB Key  Inc Key DB Name  DB ID            STATUS  Reset SCN  Reset Time
------- ------- -------- ---------------- --- ---------- ----------
1       1       AMY      1205246033       PARENT  1335270    29-APR-14
2       2       AMY      1205246033       CURRENT 1335271    29-APR-14

第五步：验证逻辑dg:

SQL> select * from v$logstdby_progress;

APPLIED_SCN APPLIED_T RESTART_SCN RESTART_T LATEST_SCN LATEST_TI MINING_SCN MINING_TI RESETLOGS_ID
----------- --------- ----------- --------- ---------- --------- ---------- --------- ------------
    1335268               1334503              1334503    
    
SQL>  select process,status,sequence# from v$managed_standby;

PROCESS   STATUS        SEQUENCE#
--------- ------------ ----------
ARCH      CONNECTED             0
ARCH      CONNECTED             0
ARCH      CONNECTED             0
ARCH      CONNECTED             0
ARCH      CONNECTED             0

SQL>


咦？发现问题了，查看主数据库日志：

Error 1017 received logging on to the standby
------------------------------------------------------------
Check that the primary and standby are using a password file
and remote_login_passwordfile is set to SHARED or EXCLUSIVE, 
and that the SYS password is same in the password files.
      returning error ORA-16191
------------------------------------------------------------
PING[ARC1]: Heartbeat failed to connect to standby ‘dg2‘. Error is 16191.

密码文件的问题咯
重建密码文件？那应该是在10G但是到11g不能重建，我们要做的是将主库的密码 文件copy到备库，然后mv。
之后查看主库日志 状态如下(可以发现主库每隔1分钟去主动ping一下备库）：

------------------------------------------------------------
PING[ARC1]: Heartbeat failed to connect to standby ‘dg2‘. Error is 16191.
Tue Apr 29 22:39:42 2014
Error 1017 received logging on to the standby
------------------------------------------------------------
Check that the primary and standby are using a password file
and remote_login_passwordfile is set to SHARED or EXCLUSIVE, 
and that the SYS password is same in the password files.
      returning error ORA-16191
------------------------------------------------------------
PING[ARC1]: Heartbeat failed to connect to standby ‘dg2‘. Error is 16191.
Tue Apr 29 22:40:46 2014
******************************************************************
LGWR: Setting ‘active‘ archival for destination LOG_ARCHIVE_DEST_2
******************************************************************
LGWR: Standby redo logfile selected for thread 1 sequence 84 for destination LOG_ARCHIVE_DEST_2
Thread 1 advanced to log sequence 84 (LGWR switch)
  Current log# 3 seq# 84 mem# 0: /u01/app/oracle/oradata/dg/redo03.log
Tue Apr 29 22:40:49 2014
Archived Log entry 138 added for thread 1 sequence 83 ID 0x68b85302 dest 1:
Tue Apr 29 22:40:49 2014
ARC3: Standby redo logfile selected for thread 1 sequence 83 for destination LOG_ARCHIVE_DEST_2

查看备库日志：

LOGMINER: Read buffers: 16
LOGMINER: Memory LWM: limit 10M, LWM 24M, 80%
LOGMINER: Memory Release Limit: 1M
RFS LogMiner: Registered logfile [/u01/app/oracle/fast_recovery_area/DG2/foreign_archivelog/DG1/2014_04_29/o1_mf_1_82_9ozghfdo_.arc] to LogMiner session id [1]
RFS LogMiner: Registered logfile [/u01/app/oracle/fast_recovery_area/DG2/foreign_archivelog/DG1/2014_04_29/o1_mf_1_81_9ozghffw_.arc] to LogMiner session id [1]
Tue Apr 29 22:40:47 2014
Primary database is in MAXIMUM PERFORMANCE mode
RFS[4]: Assigned to RFS process 3779
RFS[4]: Selected log 4 for thread 1 sequence 84 dbid 1756848898 branch 843517891
Tue Apr 29 22:40:48 2014
RFS[5]: Assigned to RFS process 3777
RFS[5]: Opened log for thread 1 sequence 79 dbid 1756848898 branch 843517891
RFS LogMiner: Registered logfile [/u01/app/oracle/fast_recovery_area/DG2/foreign_archivelog/DG1/2014_04_29/o1_mf_1_79_9ozghhy9_.arc] to LogMiner session id [1]
Tue Apr 29 22:40:50 2014
LOGMINER: session#=1 (Logical_Standby$), reader MS00 pid=38 OS id=3781 sid=44 started
Tue Apr 29 22:40:50 2014
LOGMINER: session#=1 (Logical_Standby$), builder MS01 pid=39 OS id=3783 sid=45 started
Tue Apr 29 22:40:50 2014
LOGMINER: session#=1 (Logical_Standby$), preparer MS02 pid=40 OS id=3785 sid=48 started
Tue Apr 29 22:40:50 2014
RFS LogMiner: RFS id [3787] assigned as thread [1] PING handler
Tue Apr 29 22:40:51 2014
RFS[6]: Assigned to RFS process 3789
RFS[6]: Selected log 5 for thread 1 sequence 83 dbid 1756848898 branch 843517891
Tue Apr 29 22:40:55 2014
RFS LogMiner: Registered logfile [/u01/app/oracle/fast_recovery_area/DG2/foreign_archivelog/DG1/2014_04_29/o1_mf_1_83_9ozghp29_.arc] to LogMiner session id [1]
LOGMINER: Begin mining logfile during dictionary load for session 1 thread 1 sequence 79, /u01/app/oracle/fast_recovery_area/DG2/foreign_archivelog/DG1/2014_04_29/o1_mf_1_79_9ozghhy9_.arc
Tue Apr 29 22:41:09 2014
Thread 1 advanced to log sequence 2 (LGWR switch)
  Current log# 2 seq# 2 mem# 0: /u01/app/oracle/oradata/dg/DG2/onlinelog/o1_mf_2_9ozd8zc1_.log
Tue Apr 29 22:41:11 2014
Archived Log entry 1 added for thread 1 sequence 1 ID 0x47d6f0d0 dest 1:
Tue Apr 29 22:41:20 2014
Thread 1 advanced to log sequence 3 (LGWR switch)
  Current log# 3 seq# 3 mem# 0: /u01/app/oracle/oradata/dg/DG2/onlinelog/o1_mf_3_9ozd904o_.log
Tue Apr 29 22:41:22 2014
Archived Log entry 2 added for thread 1 sequence 2 ID 0x47d6f0d0 dest 1:
Thread 1 cannot allocate new log, sequence 4
Checkpoint not complete
  Current log# 3 seq# 3 mem# 0: /u01/app/oracle/oradata/dg/DG2/onlinelog/o1_mf_3_9ozd904o_.log
Thread 1 advanced to log sequence 4 (LGWR switch)
  Current log# 1 seq# 4 mem# 0: /u01/app/oracle/oradata/dg/DG2/onlinelog/o1_mf_1_9ozd8yhq_.log
Tue Apr 29 22:41:31 2014
Archived Log entry 3 added for thread 1 sequence 3 ID 0x47d6f0d0 dest 1:
Tue Apr 29 22:41:47 2014
RFS LogMiner: RFS id [3787] assigned as thread [1] PING handler

确认进程：

SQL> select process,status,sequence# from v$managed_standby;

PROCESS   STATUS        SEQUENCE#
--------- ------------ ----------
ARCH      CLOSING               2
ARCH      CLOSING               3
ARCH      CONNECTED             0
ARCH      CLOSING              83
ARCH      CLOSING               1
RFS       IDLE                  0
RFS       IDLE                  0
RFS       IDLE                  0
RFS       IDLE                  0
RFS       IDLE                 84

10 rows selected.

SQL>

至此完成逻辑dg的搭建过程：


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