Re: Joined Logicals

[John Earl <johnearl@xxxxxxxxxxx>]

Marie,


Graziano, Marie wrote:
> 
> I have a scenario where the V.P. wants us to create Joined logicals with
> SQL.  Can someone give me some feedback why I would NOT want to have joined
> logicals.
> 
> The files would be ½ million records +.


It depends.   Would the access paths be permanent or does he
want to create these JLF's on the fly?  

Creating any access path (LF or JLF) on the fly over
500,000+ records is no light matter.  The perfomance
implications could be quite noticable (especially on a
smaller system).  

But if these are fairly static definitions, and the VP just
want's one or two JLF's to support some business function,
then build the access paths.  The overhead will not be much
different than creating a similar sized LF.

If the requests would be dynamic and the JLF's need to be
built on the fly, it is usually more efficient to perform an
initial query that does record selection to an outfile. 
Then build the JLF over the outfile which would contains a
significanly smaller set of data than the original 500,000+
record data file.

hth,

jte



> 
> Mgraziano@badgermeter.com
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John Earl                       johnearl@toolnet.com

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