Oracle数据库 DGbroker三种保护模式的切换

前端技术 2023/09/01 Oracle

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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