[dba-SQLServer] Logical reads/writes

Arthur,  I'm assuming that you've answered your own question via Google, but
in case you hadn't and since I haven't seen any responses to this message
I'd thought I'd post an answer...

http://msdn.microsoft.com/en-us/library/aa224763(SQL.80).aspx

<snip>
Data is read from the database disk files into the buffer cache. Multiple
logical reads of the data can be satisfied without requiring that the data
be physically read again. The data remains in the cache until it has not
been referenced for some time and the database needs the buffer area to read
in more data. Data is written back to disk only if it is modified. Data can
be changed multiple times by logical writes before a physical write
transfers the new data back to disk.
</snip>

so yes to answer your question a logical read is read from memory as opposed
to disk.

-Francisco
http://sqlthis.blogspot.com | Tsql and More...


On Tue, Sep 23, 2008 at 8:51 AM, Arthur Fuller <fuller.artful at gmail.com>wrote:

> I suppose that I should know what these terms mean, but the fact is that I
> don't.  I'm looking at this report of object execution times from SQL 2005
> and  there are columns about logical reads and writes and I have no idea
> what that means. Logical as opposed to physical, or as opposed to
> illogical?
> Oh and then there is Total Logical IO. That would be a really funny graph
> if
> they had Illogical Reads and Writes LOL.
>
> It's time to Google, I guess.
>
> Arthur
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