Re: Indexed PF vs. LF performance -- MIDRANGE-L

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Hi Tim

I can't imagine it being much different - an index in a PF is in a separate space object on the system from the data itself - and an LF is just a different space object. Both will have entries in a tree that point to RRNs in the PF.

Sometimes we don't remember that PFs are compound objects - they are made up of several different kinds of low-level object types - *MBR, *FMT, etc. You can do a DMPOBJ of a PF and get and idea of all these things. BTW, DMPOBJ does not show you the actual raw data as stored - you have to dig into SST to do that.

I guess one thing is to make a test - I mean, if it's 2 billion operations, it might matter - 100? Naw!

HTH
Vern

On 7/30/2012 3:19 PM, Tim Adair wrote:

A colleague asked me about this and I haven't been able to find any
definitive information.

For RPG (IV, but not ILE) doing CHAINs, SETLLs, and READs - which is faster,
an indexed PF or a flat PF with an LF defined with the key? For the sake of
this question, let's assume we're talking about a single key field. The
file is DDS-defined, and must remain that way for now. And for this example
we're not interested in rewriting the RPG using SQL.

We're on 7.1.

Thoughts please?

TIA.

~TA~

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