Database – “Dirty Reads” / Read Un-committed data

Database – “Dirty Reads” / Read Un-committed data

Recently, noticed that our Database was running very slowly.

It took a little while, but with time was able to identify the “offending” queries.

As the conversation with the Query Designer evolved, I heard him muted what is the big deal, I have (no lock) on the Queries.

A couple of weeks ago, I would have concurred, but once one works on VLDB systems; one would have to think a bit more.  What is the big deal.

Well, Dirty read (no luck), “merely” means do not block other users reads and writes.

The Query still:

  1. Reads just as many records
  2. Uses similar amount of resources such as (IO /CPU / Memory) omitting resources taking for latches and locks

So next time you see “no lock” do not assume that the Query does no HARM.

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