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Oracle数据库 DGbroker三种保护模式的切换

发布时间:2015-12-22 作者:vijayfly 来源:转载
这篇文章主要介绍了Oracle数据库DGbroker三种保护模式的切换的相关资料,需要的朋友可以参考下

1.三种保护模式

– Maximum protection

在Maximum protection下, 可以保证从库和主库数据完全一样,做到zero data loss.事务同时在主从两边提交完成,才算事务完成。如果从库宕机或者网络出现问题,主从库不能通讯,主库也立即宕机。在这种方式下,具有最高的保护等级。但是这种模式对主库性能影响很大,要求高速的网络连接。

– Maximum availability

在Maximum availability模式下,如果和从库的连接正常,运行方式等同Maximum protection模式,事务也是主从库同时提交。如果从库和主库失去联系,则主库自动切换到Maximum performance模式下运行,保证主库具有最大的可用性。

– Maximum performance

在Maximum performance,主库把归档的 archived log通过arch进程传递给从库,在这种方式下,主库运行性能最高,但是不能保证数据不丢失,且丢失的数据受redo log的大小影响。在redo log过大的情况下,可能一天都没有归档一个日志,可以通过手工切换日志的方式来减小数据的丢失。

2.模式切换(Maximum performance切换至Maximum availability)

a.查看保护的模式

DGbroker查看:

DGMGRL> show configuration verbose;
Configuration - dgc
 Protection Mode: MaxPerformance
 Databases:
 atest1 - Primary database
 atest2 - Physical standby database
 Properties:
 FastStartFailoverThreshold  = '30'
 OperationTimeout    = '30'
 FastStartFailoverLagLimit  = '30'
 CommunicationTimeout   = '180'
 ObserverReconnect    = '0'
 FastStartFailoverAutoReinstate = 'TRUE'
 FastStartFailoverPmyShutdown = 'TRUE'
 BystandersFollowRoleChange  = 'ALL'
 ObserverOverride    = 'FALSE'
 ExternalDestination1   = ''
 ExternalDestination2   = ''
 PrimaryLostWriteAction   = 'CONTINUE'
Fast-Start Failover: DISABLED
Configuration Status:
SUCCESS 

sqlplus查看:

SQL> select database_role,protection_mode,protection_level from v$database;
DATABASE_ROLE  PROTECTION_MODE  PROTECTION_LEVEL
---------------- -------------------- --------------------
PRIMARY  MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE 

b.查看备库的日志传输模式(参数LogXptMode(sync:同步传输/async:异步传输))

DGMGRL> show database verbose 'atest2';
Database - atest2
 Role:   PHYSICAL STANDBY
 Intended State: APPLY-ON
 Transport Lag: 0 seconds (computed 1 second ago)
 Apply Lag:  0 seconds (computed 1 second ago)
 Apply Rate:  97.00 KByte/s
 Real Time Query: ON
 Instance(s):
 atest
 Properties:
 DGConnectIdentifier    = 'atest2'
 ObserverConnectIdentifier  = ''
 LogXptMode      = 'sync'
 DelayMins      = '0'
 Binding       = 'optional'
 MaxFailure      = '0'
 MaxConnections     = '1'
 ReopenSecs      = '300'
 NetTimeout      = '30'
 RedoCompression     = 'DISABLE'
 LogShipping      = 'ON'
 PreferredApplyInstance   = ''
 ApplyInstanceTimeout   = '0'
 ApplyParallel     = 'AUTO'
 StandbyFileManagement   = 'AUTO'
 ArchiveLagTarget    = '0'
 LogArchiveMaxProcesses   = '4'
 LogArchiveMinSucceedDest  = '1'
 DbFileNameConvert    = ''
 LogFileNameConvert    = ''
 FastStartFailoverTarget   = ''
 InconsistentProperties   = '(monitor)'
 InconsistentLogXptProps   = '(monitor)'
 SendQEntries     = '(monitor)'
 LogXptStatus     = '(monitor)'
 RecvQEntries     = '(monitor)'
 ApplyLagThreshold    = '0'
 TransportLagThreshold   = '0'
 TransportDisconnectedThreshold = '30'
 SidName       = 'atest'
 StaticConnectIdentifier   = '(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=vijay02.database.com)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=atest2_DGMGRL)(INSTANCE_NAME=atest)(SERVER=DEDICATED)))'
 StandbyArchiveLocation   = '/u01/app/oracle/oradata/ATEST/archivelog'
 AlternateLocation    = ''
 LogArchiveTrace     = '0'
 LogArchiveFormat    = '%t_%s_%r.dbf'
 TopWaitEvents     = '(monitor)'
Database Status:
SUCCESS 

c.如果LogXptMode的值为async,就要将其修改为sync

DGMGRL> edit database atest1 set property logxptmode=sync;
Property "logxptmode" updated 

d.修改完之后再次确认LogXptMode的值,如步骤b

e.切换模式(如果切换失败,则再次去确认备库LogXptMode的值)

DGMGRL> edit configuration set protection mode as maxavailability;
Succeeded.

f. 确认数据库的的保护模式,如步骤a

g.需要注意的是,步骤c中修改的sync是备库的值,切记!

3.个人小结:

a.三种模式在可以在DGbroker中自由切换(使用步骤2的方式)(在测试库中),正常情况下,数据库能迅速反应过来(查看保护模式的时候)。

b.使用Maximum performance的时候,参数(备库)LogXptMode设置为async就好/

c.使用Maximum protection或者Maximum availability的时候,参数(备库)LogXptMode要设置为sync。

d.(经测试)使用Maximum protection时,当备库出现异常(如网络问题,数据库宕机),主库会挂起(告警日志会报如下错误),当备库恢复正常之后,主库也会恢复。

LGWR: Error 1034 attaching to RFS for reconnect

e.使用Maximum protection时,在当备库出现异常的情况下,当主库挂起时,(主库)可以强制切换到 Maximum performance,但当重新切回Maximum protection(在备库恢复时),主库需重启。

DGMGRL> edit configuration set protection mode as maxprotection;
Operation requires shutdown of instance "atest" on database "atest1"
Shutting down instance "atest"...
Unable to connect to database
ORA-12545: Connect failed because target host or object does not exist
Failed.
Warning: You are no longer connected to ORACLE.
Please complete the following steps to finish the operation:
 shut down instance "atest" of database "atest1"
 start up instance "atest" of database "atest1"

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