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Exam 70-458 – Objective 3 – Implement high availability

Implement AlwaysOn

Implement database mirroring (http://technet.microsoft.com/en-us/library/ms189852.aspx)

Implement replication (http://technet.microsoft.com/en-us/library/ms151198.aspx)

  • Troubleshoot replication problems (http://technet.microsoft.com/en-us/library/ms151756(v=sql.105).aspx)
  • Identify appropriate replication strategy (http://technet.microsoft.com/en-us/library/ms152531.aspx)
    • Snapshot –  when data changes are substantial but infrequent (http://technet.microsoft.com/en-us/library/ms151832.aspx)
      • Data changes infrequently.
      • Replicating small volumes of data.
      • A large volume of changes occurs over a short period of time.
    • Transactional (http://technet.microsoft.com/en-us/library/ms151176.aspx)
      • You want incremental changes to be propagated to Subscribers as they occur.
      • The application requires low latency between the time changes are made at the Publisher and the changes arrive at the Subscriber.
      • The application requires access to intermediate data states. For example, if a row changes five times, transactional replication allows an application to respond to each change (such as firing a trigger), not simply the net data change to the row.
      • The Publisher has a very high volume of insert, update, and delete activity.
      • The Publisher or Subscriber is a non-SQL Server database, such as Oracle.
    • Peer-to-peer (http://technet.microsoft.com/en-us/library/ms151196.aspx)
      • Catalog queries and other reads are spread across multiple nodes. This enables performance to remain consistent as reads increase.
      • If one of the nodes in the system fails, an application layer can redirect the writes for that node to another node. This maintains availability.
      • If a node requires maintenance or the whole system requires an upgrade, each node can be taken offline and added back to the system without affecting the availability of the application.
    • Merge (http://technet.microsoft.com/en-us/library/ms152746.aspx)
      • Multiple Subscribers might update the same data at various times and propagate those changes to the Publisher and to other Subscribers.
      • Subscribers need to receive data, make changes offline, and later synchronize changes with the Publisher and other Subscribers.
      • Each Subscriber requires a different partition of data.
      • Conflicts might occur and, when they do, you need the ability to detect and resolve them.
      • The application requires net data change rather than access to intermediate data states. For example, if a row changes five times at a Subscriber before it synchronizes with a Publisher, the row will change only once at the Publisher to reflect the net data change (that is, the fifth value).

Preparation resources

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