July 11, 2012
-- Why is client failover so important that all these explicit precautions and steps during configuration and coding need to be taken? These extra steps take up more time and resources, delaying application rollout in the eye of the management. By properly justifying these tasks before hand and incorporating them in the overall plan and schedule, this perception of delay can be eliminate altogether. Reliable 24/7 operation cannot be achieved merely by providing redundancy at the database level. The clients need to be configured to switch over and use the redundant resources in a timely fashion when the primary resources fail. During a failure, client sessions normally lose transactions that remain uncommitted and are also subjected to wastage of time, as they realize that their database session has failed and they have to manually reconnect to a secondary database resource. Application cluster always protect this fail over and provides excellent other features.http://www.dbametrix.com
Especially if the transaction or query is longer and running for numerous hours previous to the failure, resuming it from scrape can confirm very costly, in terms of time and money. In order to keep away from wastage of time and difficulty to end users, it is necessary to take a complete two-pronged approach, give sufficient redundancy and organize all clients to robotically switch over to redundant resource. The two major purposes of such switchover should be as following. Switch over should be crystal clear, without the client having to physically reconnect. The transactions present at the time of failure should be transported to the secondary database resource with as small loss as likely. Wherever suitable, the present situation of the transactions should be concluded and only the leftover segments should have to be executing on the secondary database resource.http://www.kendba.com/books/interview-questions-books/
Of these intentions, the subsequent is fairly complicated to convince in its whole. Certain sections of transactions can be re-executed. However, precisely determining where the transaction not succeeded and switching only the remaining section over is a discouraging job and necessitates the resolution to be highly complicated. Currently accessible resolutions assist to move only SELECT statements over. All uncommitted changes lean to get lost and need to be rerun.
In 24/7 running large databases, this circumstances is very serious and mainly essential. Handling application failover is necessary for providing improved services to every customer. Application switchover should be transparent and providing better security and consistency. Every banking sector, telecommunication sectors, and other financial services badly need this option. It is very useful to deploy client failover and switchover using applications.