邏輯standby用的很少,特別是在11g,物理standby也可以只讀開啟並實時應用,物理standby也可以做滾動升級.不過,最近有一個使用者需求,要建一個報表系統資料庫,
想到可以試試邏輯standby去實現,同步生產庫的基礎資料使用者,並在邏輯standby上建BI相關的使用者,用做資料統計.這樣可以避免直接透過dblink或物化檢視抓取資料對生
產庫的效能影響,又比利用goldengate實現同步在維護性上方便.

一.建立邏輯standby官方文件及註釋:
Step by Step Guide on How to Create Logical Standby (文件 ID 738643.1)

Applies to:

Oracle Database - Enterprise Edition - Version 10.2.0.1 to 12.1.0.2 [Release 10.2 to 12.1]
Information in this document applies to any platform.
***Checked for relevance on 21-Sep-2012***
*** Reviewed for Relevance 16-Jul-2015 ***

Goal

Step by Step Guide on How to Create Logical Standby

Solution

Prerequisite
--必要條件
1 : Before setting up a logical standby database, ensure the logical standby database can maintain the data types and tables in your primary database. See Appendix C of the dataguard documentation for a complete list of data type and storage type considerations.
--確定資料庫中的資料型別和儲存型別支援
2 : Ensure Table Rows in the Primary Database Can Be Uniquely Identified.
--確定表中各行的唯一性,儘量有主鍵或唯一索引
2.1 : Find Tables Without Unique Logical Identifier in the Primary Database.

Use following query to display a list of tables that SQL Apply may not be able to uniquely identify:

SQL> SELECT OWNER, TABLE_NAME FROM DBA_LOGSTDBY_NOT_UNIQUE WHERE (OWNER, TABLE_NAME) NOT IN (SELECT DISTINCT OWNER, TABLE_NAME FROM DBA_LOGSTDBY_UNSUPPORTED) AND BAD_COLUMN = 'Y'

2.2 : If your application ensures the rows in a table are unique, you can create a disabled primary key RELY constraint on the table. Use ALTER TABLE command to add a disabled primary-key RELY constraint.
The following example creates a disabled RELY constraint on a table named mytab, for which rows can be uniquely identified using the id and name columns:

SQL> ALTER TABLE mytab ADD PRIMARY KEY (id, name) RELY DISABLE;

Creating a Logical Standby Database:
--建立邏輯standby
Step 1 Create a Physical Standby Database
--建邏輯standby,要先建一個物理standby,然後再進行轉換
Create a Physical Standby Database and make sure that there is no error in remote archiving to Standby from Primary Database.

Please refer following documentations for creating physical standby database:

For 10.2:
Oracle? Data Guard Concepts and Administration 10g Release 2 (10.2)

Step 2 Make Sure that Physical Standby is in Sync with Primary Database
--在物理standby上執行,檢視跟主庫的同步情況
Use following query on Standby to check:

SQL>SELECT ARCH.THREAD# "Thread", ARCH.SEQUENCE# "Last Sequence Received", APPL.SEQUENCE# "Last Sequence Applied"
FROM
(SELECT THREAD# ,SEQUENCE# FROM V$ARCHIVED_LOG WHERE (THREAD#,FIRST_TIME ) IN (SELECT THREAD#,MAX(FIRST_TIME) FROM V$ARCHIVED_LOG GROUP BY THREAD#)) ARCH,
(SELECT THREAD# ,SEQUENCE# FROM V$LOG_HISTORY WHERE (THREAD#,FIRST_TIME ) IN (SELECT THREAD#,MAX(FIRST_TIME) FROM V$LOG_HISTORY GROUP BY THREAD#)) APPL
WHERE
ARCH.THREAD# = APPL.THREAD#
ORDER BY 1;
/*
Thread Last Sequence Received Last Sequence Applied
1 60 60
*/

There should not be any difference in Last Seq Received and Last Seq Applied on Physical Standby.

Step 3 Stop Redo Apply on the Physical Standby Database
--停止物理standby的redo應用

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;

Step 4 Set Parameters for Logical Standby in Primary
--設定主庫的日誌歸檔目錄,LOG_ARCHIVE_DEST_3的設定是為了主庫切換後使用
4.1. Change VALID_FOR in LOG_ARCHIVE_DEST_1 on Primary to (ONLINE_LOGFILES,ALL_ROLES)

LOG_ARCHIVE_DEST_1= 'LOCATION=/u01/arch/online/ VALID_FOR=(ONLINE_LOGFILES,ALL_ROLES) DB_UNIQUE_NAME=prim1'

4.2. Set LOG_ARCHIVE_DEST_3 for logs which will received on Standby from Primary

LOG_ARCHIVE_DEST_3= 'LOCATION=/u01/arch/standby/ VALID_FOR=(STANDBY_LOGFILES,STANDBY_ROLE) DB_UNIQUE_NAME=prim1'
LOG_ARCHIVE_DEST_STATE_3=ENABLE

Note: LOG_ARCHIVE_DEST_3 only takes effect when the primary database is transitioned to the logical standby role.

Step 5 Build a Dictionary in the Redo Data on Primary Database
--在主庫上生成logminer字典資訊

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.

Step 6 Convert to a Logical Standby Database
--轉換物理standby到邏輯standby,db_name是要指定一個新的邏輯standby 的db_name

SQL> ALTER DATABASE RECOVER TO LOGICAL STANDBY <db_name>;

For db_name, specify a database name to identify the new logical standby database. If you are using a spfile for standby, then command will update the db_name parameter otherwise it will issues a message reminding you to set the name of the DB_NAME parameter after shutting down the database.

Step 7 Create a New Password File for Logical Standby Database
--新建密碼檔案,這個在10g需要執行,11g原有的就可以

$ORAPWD FILE=<filename> PASSWORD=<password> ENTRIES=<max_users>

This step is required in 10.2 only and should not be performed in 11g.

Step 8 Shutdown and Startup Logical Standby Database in Mount Stage
--關閉邏輯standby並開戶到mount狀態

SQL> SHUTDOWN;
SQL> STARTUP MOUNT;

Step 9 Adjust Initialization Parameter on Logical Standby Database
--轉換為邏輯standby後,修改原有的日誌歸檔目錄

LOG_ARCHIVE_DEST_1= 'LOCATION=/u01/arch/online/ VALID_FOR=(ONLINE_LOGFILES,ALL_ROLES) DB_UNIQUE_NAME=logstd1'
LOG_ARCHIVE_DEST_2= 'SERVICE=prim1 LGWR ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=prim1'
LOG_ARCHIVE_DEST_3= 'LOCATION=/u01/arch/standby/ VALID_FOR=(STANDBY_LOGFILES,STANDBY_ROLE) DB_UNIQUE_NAME=logstd1'
LOG_ARCHIVE_DEST_STATE_1=ENABLE
LOG_ARCHIVE_DEST_STATE_2=ENABLE
LOG_ARCHIVE_DEST_STATE_3=ENABLE

Step 10 Open the Logical Standby Database
--以resetlogs方式開啟資料庫

SQL> ALTER DATABASE OPEN RESETLOGS;

Step 11 Start Logical Apply on Standby
--開啟sql apply,這裡的immediate是要實時應用,需要有standby redo log支援,如果不需要實時應用,可不加immediate.

SQL> ALTER DATABASE START LOGICAL STANDBY APPLY IMMEDIATE;

二.邏輯standby建立完成後的一些設定
--在邏輯standby上將guard設定為standby,實現能在邏輯standby建立BI相關的使用者
SQL>alter database guard standby;
--在邏輯standby上使用dbms_logstdby.skip跳過不需要同步的使用者的表
SQL>alter database stop logical standby apply;
SQL>exec dbms_logstdby.skip(stmt=>'SCHEMA_DDL',SCHEMA_NAME=>'HR',OBJECT_NAME=>'%');
SQL>exec dbms_logstdby.skip(stmt=>'DML',SCHEMA_NAME=>'HR',OBJECT_NAME=>'%');
SQL>alter database start logical standby apply;
   如果將來需要將跳過的表重新新增回來
   SQL>alter database stop logical standby apply;
   透過exec dbms_logstdby.unskip新增回來
   透過dbms_logstdby.instantiate_table同步,這裡需要建dblink
   SQL>alter database start logical standby apply;

透過Oracle 11g 邏輯standby實現BI的需求

Applies to:

Goal

Solution

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