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Message Posted: Wed, 09 Jan 2008 @ 13:17:14 GMT

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Hi,

We run a heartbeat query on the hour every hour 24/7 365 on our Production, Backup and Development machines.

The query takes anything from about 30 seconds to over an hour depending on how busy the machine is (avg about 2 mins) but we find it a useful metric to measure how busy the machine is and to spot for possible performance impacts.

The query that we run is a perfect example of how NOT to write SQL, a few unions and cross joins of two 1000 row tables and some inefficient ranking functions put in for good measure. If you have a a query that runs in 1 sec on a quite machine and 5 sec on a busy machine you can't really tell that the machine is running 5 times slower, so we wanted a query that ran a bit slower when the machine was quite and for a while when the machine is busy.

We think that the impact of this query running every hour is worth it for the metric�'s that we can get from the results.

Hope this helps.

Fachtna O'Donovan
Software Engineer
AIB Bank
Ireland

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