## Oracle19c Data Guard Broker
---
### 描述
- Data Guard broker是一個集中的框架，用於透過客戶端連線到配置中的任何資料庫來管理整個Data Guard配置
- DGMGRL無法建立備用（GUI可以這樣做）。CLI主要用於配置和管理。
- 使用一個命令輕鬆切換/故障切換，從而最大限度地減少與計劃內/計劃外停機相關的總體停機時間
- broker不使用各種SQL*Plus語句管理主資料庫和備用資料庫，而是提供單一的統一配置
- 代理將其配置詳細資訊儲存在平面檔案中。這些檔案儲存在資料保護配置中的每個資料庫節點上。此外，配置檔案的兩個副本始終儲存在每個資料庫上以備冗餘。
- 下面的引數控制配置檔案的儲存位置。
```
DG_BROKER_CONFIG_FILE1 & DG_BROKER_CONFIG_FILE2
```

### 新特性
>  #### oracle19c

- 動態更改fast-start failover目標，而無需禁用
- 在不影響當前環境下，可使用觀察模式(observe-only mode)模擬測試fast-start failover工作方式
- Broker配置資訊可以匯出作為備份，當需要重建Broker時，可以使用匯出的備份匯入。
- 新命令可用於設定、修改和顯示資料庫、遠同步例項或恢復裝置中資料庫初始化引數的值。使用這些命令設定的值將直接應用於資料庫，而不會儲存在代理配置檔案中。

>  ####  不推薦的功能

- 以下與資料庫初始化引數相關聯的屬性在此版本中不推薦使用，在將來的版本中可能會被取消支援。這些屬性將不再儲存在代理配置檔案中。

```
ArchiveLagTarget, DataGuardSyncLatency,LogArchiveMaxProcesses,xixLogArchiveMinSucceedDest, LogArchiveTrace,StandbyFileManagement,DbFileNameConvert, LogArchiveFormat, LogFileNameConvert
```
- 不一致屬性在此版本中棄用。此屬性將始終沒有值。
- 以下與邏輯備用相關的屬性將被重新計算，並可能在將來的版本中被取消支援:

```
LsbyMaxEventsRecorded, LsbyMaxServers,LsbyMaxSga, LsbyPreserveCommitOrder, LsbyRecordAppliedDdl,LsbyRecordSkipDdl,LsbyRecordSkipErrors, and LsbyParameter
```
> #### 不再支援的特性

- MaxConnections 引數不再支援

### dg broker 配置

> #### 環境準備

- > > 網路配置

```
--主備參考，主要注意GLOBAL_DBNAME，db_unique_name+DGMGRL
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = mydbdg)
        (ORACLE_HOME = /u01/app/oracle/product/19.0.0/dbhome_1)
      (SID_NAME = mydbdg)
    )
    (SID_DESC =
      (GLOBAL_DBNAME = mydbdg_DGMGRL)
        (ORACLE_HOME = /u01/app/oracle/product/19.0.0/dbhome_1)
      (SID_NAME = mydbdg)
    )  
  )
```

- > > 引數，使用者環境

```
--主端執行即可
--解鎖dg使用者,必須賦權sysdg許可權，否則因無法寫入密碼檔案而無法遠端等。
 select username,SYSBACKUP, SYSDG from V$PWFILE_USERS;
alter user sysdg identified by oracle account unlock;
grant sysdg to sysdg;
 select username,SYSBACKUP, SYSDG from V$PWFILE_USERS;

--修改引數，主備庫
alter system set dg_broker_start=true;

--測試連線
[oracle@node216 admin]$ dgmgrl 
DGMGRL for Linux: Release 19.0.0.0.0 - Production on Tue Feb 18 15:14:07 2020
Version 19.3.0.0.0

Welcome to DGMGRL, type "help" for information.
DGMGRL> connect sysdg
Password:
Connected to "mydb19c"
Connected as SYSDG.
DGMGRL> connect sysdg@mydbdg
Password:
Connected to "MYDBDG"
Connected as SYSDG.
DGMGRL> 
```
> #### 開始配置

- 主端建立配置資訊

```
create configuration 'mycdb' as primary database is 'mydb19c' connect identifier is mydb19c;
--檢視
DGMGRL> show configuration;

Configuration - mycdb

Protection Mode: MaxPerformance
  Members:
  mydb19c - Primary database

Fast-Start Failover:  Disabled

Configuration Status:
DISABLED
```

- 備端加入配置資訊

```
--備端清除遠端資訊，不然報錯,後續切換時該引數自動設定
 alter system set LOG_ARCHIVE_DEST_2='';
  Add database 'mydbdg' as connect identifier is mydbdg maintained as physical;

--檢查配置資訊
DGMGRL> show configuration;

Configuration - mycdb

Protection Mode: MaxPerformance
  Members:
  mydb19c - Primary database
    mydbdg  - Physical standby database

Fast-Start Failover:  Disabled

Configuration Status:
DISABLED

--檢視資料庫相信配置資訊
SHOW DATABASE VERBOSE 'South_Sales'
--修改參考命令
EDIT DATABASE 'South_Sales' SET PROPERTY 'LogArchiveFormat'='log_%t_%s_%r_%d.arc';
EDIT DATABASE 'South_Sales' SET PROPERTY 'StandbyArchiveLocation'='/archfs/arch/';
```

- 啟動配置

```
DGMGRL> ENABLE CONFIGURATION;
Enabled.
DGMGRL> show configuration;

Configuration - mycdb

Protection Mode: MaxPerformance
  Members:
  mydb19c - Primary database
    mydbdg  - Physical standby database

Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS   (status updated 6 seconds ago)

DGMGRL>

--檢查資料庫資訊
DGMGRL> show database 'mydbdg';

Database - mydbdg

Role:               PHYSICAL STANDBY
  Intended State:     APPLY-ON
  Transport Lag:      0 seconds (computed 0 seconds ago)
  Apply Lag:          0 seconds (computed 0 seconds ago)
  Average Apply Rate: 3.00 KByte/s
  Real Time Query:    ON
  Instance(s):
    mydbdg

Database Status:
SUCCESS

DGMGRL> show database 'mydb19c';

Database - mydb19c

Role:               PRIMARY
  Intended State:     TRANSPORT-ON
  Instance(s):
    mydb19c

Database Status:
SUCCESS
```
> #### 主備切換

- dgmgrl檢查資訊

```
--驗證主資料庫
DGMGRL> VALIDATE DATABASE 'mydb19c';

Database Role:    Primary database

Ready for Switchover:  Yes

Flashback Database Status:
    mydb19c:  Off

Managed by Clusterware:
    mydb19c:  NO             
    Validating static connect identifier for the primary database mydb19c...
    The static connect identifier allows for a connection to database "mydb19c".
--備庫
DGMGRL> VALIDATE DATABASE 'mydbdg';

Database Role:     Physical standby database
  Primary Database:  mydb19c

Ready for Switchover:  Yes
  Ready for Failover:    Yes (Primary Running)

Flashback Database Status:
    mydb19c:  Off
    mydbdg :  Off

Managed by Clusterware:
    mydb19c:  NO             
    mydbdg :  NO             
    Validating static connect identifier for the primary database mydb19c...
    The static connect identifier allows for a connection to database "mydb19c".

Current Log File Groups Configuration:
    Thread #  Online Redo Log Groups  Standby Redo Log Groups Status       
              (mydb19c)               (mydbdg)                             
    1         3                       2                       Insufficient SRLs

Future Log File Groups Configuration:
    Thread #  Online Redo Log Groups  Standby Redo Log Groups Status       
              (mydbdg)                (mydb19c)                            
    1         3                       0                       Insufficient SRLs
    Warning: standby redo logs not configured for thread 1 on mydb19c

Transport-Related Property Settings:
    Property                        mydb19c Value            mydbdg Value
    NetTimeout                      30                       300

--其他檢查語句
show database VERBOSE 'mydb19c';

```
- sql檢查

```
SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;

SWITCHOVER_STATUS
--------------------
TO STANDBY
```

- 切換

```
SWITCHOVER TO 'mydbdg';

--參考日誌
DGMGRL> SWITCHOVER TO 'mydbdg';
Performing switchover NOW, please wait...
Operation requires a connection to database "mydbdg"
Connecting ...
Connected to "MYDBDG"
Connected as SYSDG.
New primary database "mydbdg" is opening...
Operation requires start up of instance "mydb19c" on database "mydb19c"
Starting instance "mydb19c"...
Connected to "mydb19c"
Connected to "mydb19c"
Connected to "mydb19c"
Connected to "mydb19c"
Connected to "mydb19c"
Connected to "mydb19c"
Connected to "mydb19c"
Connected to "mydb19c"
Connected to "mydb19c"
Connected to "mydb19c"
Connected to "mydb19c"
Connected to an idle instance.
ORACLE instance started.
Connected to "mydb19c"
Database mounted.
Database opened.
Connected to "mydb19c"
Switchover succeeded, new primary is "mydbdg"
```
- 切換後，恢復程式自動啟動，新備庫為只讀模式

```
select name,database_role,open_mode from v$database;SQL>

NAME	  DATABASE_ROLE    OPEN_MODE
--------- ---------------- --------------------
MYDB19C   PHYSICAL STANDBY READ ONLY WITH APPLY

SQL> show pdbs

CON_ID CON_NAME			  OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
	 2 PDB$SEED			  READ ONLY  NO
	 3 TESTPDB			  MOUNTED
	 4 MYPDB			  MOUNTED

--啟動pdb
alter pluggable database mypdb open;
```

> ### 至此，dg broker 配置及切換成功

---

#### 快速切換配置參考
- 快速故障切換，不需要人工干預，透過broker工具自動切換。

> 環境準備

```
--主備必須開啟閃回區
ALTER SYSTEM SET UNDO_RETENTION=3600 SCOPE=SPFILE;
--ALTER SYSTEM SET UNDO_MANAGEMENT='AUTO' SCOPE=SPFILE;
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
SHOW PARAMETER UNDO;
ALTER SYSTEM SET DB_FLASHBACK_RETENTION_TARGET=4320 SCOPE=BOTH;
ALTER DATABASE ARCHIVELOG;
ALTER SYSTEM SET db_recovery_file_dest_size=10g;
ALTER SYSTEM SET db_recovery_file_dest=/backup/fra;
ALTER DATABASE FLASHBACK ON;
ALTER DATABASE OPEN;
```
> 啟用

- 目的零資料丟失，修改為最大可用模式

```
DGMGRL> EDIT DATABASE 'mydb19c' SET PROPERTY 'LogXptMode'='SYNC';
DGMGRL> EDIT DATABASE 'mydbdg' SET PROPERTY 'LogXptMode'='SYNC';
DGMGRL> EDIT CONFIGURATION SET PROTECTION MODE AS MAXAVAILABILITY;
```

- 啟用 快速自動故障轉移

```
--檢查切換目標
DGMGRL> show database 'mydbdg' FastStartFailoverTarget;
  FastStartFailoverTarget = 'mydb19c'
--開啟
 enable fast_start failover;
--啟動觀察
start observer;

--檢查資料庫資訊
select name,FS_FAILOVER_STATUS,FS_FAILOVER_OBSERVER_PRESENT from v$database;
```

【DATAGUARD】Oracle19c Data Guard Broker

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