• Subject: Logical file index size too small?
  • From: Buck Calabro <mcalabro@xxxxxxxxxxxx>
  • Date: Wed, 10 Dec 1997 13:05:03 -0500

Hello again!

We've got a physical file with 2.7 million records and 10+ 
logical files built over it.  In an attempt to speed up
processing, we're analysing which logicals we can eliminate.
While doing a DSPFD, I noticed that the index size for some
of these logicals is really small: 16384.  This doesn't
make any sense because the key length is 36 bytes: I'm
expecting something closer to 95 megs!

Here's the section of DSPFD under Access Path statistics for 
logical file TRBRSQ08:

Index size  . . . . . . . . . . . . . . :             16384        
Access path valid . . . . . . . . . . . :            Yes                    
Implicit access path sharing  . . . . . :            Yes                    
  Access path journaled . . . . . . . . :            No                     
File owning access path . . . . . . . . :     COMTST200/TRBRSQ08     
Member  . . . . . . . . . . . . . . . . :            TRBRSQ08               
Shared access path attributes                                               
  Maintenance . . . . . . . . . . . . . :            *IMMED                 
  Access path recovery  . . . . . . . . :            *NO                    
  Force keyed access path . . . . . . . :            *NO                    
  Keys must be unique . . . . . . . . . :            No                     
...
Based on file . . . . . . . . . . . . . . :            TRBPHY01   
  Library . . . . . . . . . . . . . . . . :            COMTST200  
  Member  . . . . . . . . . . . . . . . . :            TRBPHY01   
  Logical file format . . . . . . . . . . :            ZTRBRS08   
  Number of index entries . . . . . . . . :               2664901 

How can this be right?  The index has 2.7 million records and 
is only 16k in size?  Another logical, TRBRSQ01 has a key length
of 4, and it looks like:

Index size  . . . . . . . . . . . . . . :                    7933952
Access path valid . . . . . . . . . . . :            Yes            
Implicit access path sharing  . . . . . :            No            
...
Based on file . . . . . . . . . . . . . . :            TRBPHY01   
  Library . . . . . . . . . . . . . . . . :            COMTST200  
  Member  . . . . . . . . . . . . . . . . :            TRBPHY01   
  Logical file format . . . . . . . . . . :            ZTRBRS01   
  Number of index entries . . . . . . . . :               2664901 
  Number of member accesses . . . . . . . :                     0

This looks much better: 2.7 million * 4 bytes = 10meg.  I've got
7.9 megs... close to what I expect.

I can see that RSQ08 is sharing it's access path, but it's being
shared with itself! 

So, my question is: what can make an access path size so much
smaller than it should be?

Buck Calabro
Commsoft

+---
| This is the Midrange System Mailing List!
| To submit a new message, send your mail to "MIDRANGE-L@midrange.com".
| To unsubscribe from this list send email to MIDRANGE-L-UNSUB@midrange.com.
| Questions should be directed to the list owner/operator: david@midrange.com
+---


This thread ...

Follow-Ups:

Follow On AppleNews
Return to Archive home page | Return to MIDRANGE.COM home page

This mailing list archive is Copyright 1997-2019 by midrange.com and David Gibbs as a compilation work. Use of the archive is restricted to research of a business or technical nature. Any other uses are prohibited. Full details are available here. If you have questions about this, please contact [javascript protected email address].