Currently working on a Webspere Business Monitor application integrating with DB2 9.5 on Linux. I’ve made a few observations.One that is interesting , particuarly as Webspere Business Monitor uses BLOBsCLOBs, relates to HADR and BLOBCLOB replication.
Database logs are used in HADR , for replicating the Primary database to the Standby database.The Primary database
will support non-logged operations , such as changes to the configuration, changes to the recovery history file and BLOBsCLOBs .But the problem – is that large BLOBsCLOBs , which cannot be logged – cannot be replicated.
Insert, update, delete operations performed on a table with CLOBsBLOBs that are larger that 1 GB cannot be logged therefore not replicated to the standby server. The space is defined on the standby server , but CLOBBLOB is not replicated.
If a CLOBBLOB is smaller than 1 GB and is logged , than this will be replicated
This raises questions about : 1)if large BLOBsCLOBs need to be maintained on the Standby Server – what procedure need to be created to maintain the Standby 2)In a failover situation , would the BLOBsCLOBS be necessary to maintain the service. Consideration needs to be given to your backup procedure, servcie levels etc 3)Is HADR the best way to maintain High Availability – there are alternatives such as Shared Disk Clustering – with Tivoli Storage Automation(TSA)
Source:Jack Vamvas
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