What is HADR?

HADR is DB2’s implementation of log shipping. Which means it’s a shared-nothing kind of product. But it is log shipping at the Log Buffer level instead of the Log File level, so it can be extremely up to date. It even has a Synchronous mode that would guarantee that committed transactions on one server would also be on another server. (in years of experience on dozens of clients, I’ve only ever seen NEARSYNC used) It can only handle two servers (there’s no adding a third in), and is active/warm spare – only with 9.7 Fixpack 1 and later can you do reads on the standby and you cannot do writes on the standby.

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Registry Variables and DB2_WORKLOAD=WC

I was happy to see the new workload registry variable in Commerce 7/DB2 9. Mostly out of laziness – it requires fewer variables to be set manually, but it also ensures that nothing major is missed (I imagine they may come up with more that won’t be added to the workload registry variable in real time). I had a whole argument with whichever part of IBM a client brought in to do a load-test performance review because I had set one of the paramters to “ON” instead of “YES”. I recently ran across this statement in the Info Center:

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