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  3. April 2003

Re: access path

Leif

I've always heard it described as a description of how to have access to the records of a file. This can be sequential or keyed, based on RRN ("keyed" on RRN?) - of course, RRN can change, a key should not - or on a key value.

It's not just an iSeries term. DB2 for various platforms also uses it. A brief google reveals the equivalency of "access path" and "index"

Access path of file was used by query. Indicates that an existing
index was chosen to process the query. (iSeries)

The graph of the access path is displayed on an IBM OS/2® or Microsoft® Windows
NT® workstation, eliminating the need to interpret the plan table output (OS/390 DB2 Visual Explain)

An unkeyed physical file (probably an iSeries-only concept) can be said to have an arrival sequence access path.

Rebuilding? Depends on what you mean. An index is maintained every time a record is added/removed from the physical file. The tree may need balancing from time to time. A complete rebuild is probably rare on the 400.

Regards

Vern

At 10:05 PM 4/23/2003 -0500, you wrote: 
I have been working on and with this machine for upwards
of two sunspot cycles, and I have a confession to make:
I see references on this list and elsewhere to an "access
path" to a file. I have studied the internals of this machine,
I have looked far and wide, but I'm still baffled: what the
h*** is an "access path"? where is it? what does it do?
Why must it be "rebuilt" at times and what does that entail?
Somebody enlighten me...




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