Linked Server vs Copy the data

  • I have two separate systems. Each uses SQL Server 2005 as the database.

    System A is the customer service system and it has customer id and shopper card number.

    System B is the Super market system and it has the shopper card number and its usage.

    Should I use linked server to find out the customer's usage based on the shopper card number? or should I copy the customer id/shopper card number table to system B each day so I can query the usage from System B?

    Thanks

  • That depends on a lot of things. Do you need the data in realtime? Like, "I need this customer's data while he's at the cash register". Or do you need it for reporting and data mining? Like, "I need to know what the most common combination of any two things purchased within one week of each other is".

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  • [font="Verdana"]The issue with using a linked server for this approach is that you create a dependency between your systems. I.e. if you customer management system goes down, then your shopper system can't read the cards (and unless the code is well written, will fall over.)

    You might consider replication for this scenario.

    [/font]

  • I would argue for replication of the data by some means. Depending on size and latency requirements, an SSIS package could be suitable too.

    I have a similar issue where I have a 2 node active\passive cluster that holds databases that the business defines as a required data - 24/7. The propblem is that there are some databases that absolutely require data on llinked server that do not have the same level of redundancy. They go down and so do a few apps. I argue for bringing the the databases onto the cluster. So many reason that this makes sense...anyway, the point is, as Bruce says, if there is a dependency and the code is not up to dealing with failure, then goodbye application.

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