Re: Logical File Rebuild time

[eric.delong@xxxxxxxxxxxxxxxxx]

>From "DB2 for OS400 Database Programming":
--------------------------------------
3.4.3.2.1 Rebuilding Access Paths
Rebuilding a database access path may take as much as one 
minute for every 10,000 records.
 
Note:  This estimate should be used until actual times for your 
       system can be calculated.
 
The following factors affect this time estimate (listed in general order 
of significance):
 
   Storage pool size.  The size of the storage pool used to rebuild 
    the access path is a very important factor.  You can improve the 
    rebuild time by running the job in a larger storage pool.
 
   The system model.  The speed of the processing unit is a key 
    factor in the time needed to rebuild an access path.
 
   Key length.  A large key length will slow rebuilding the access path 
    because more key information must be constructed and stored in 
    the access path.
 
   Select/omit values.  Select/omit processing will slow the 
    rebuilding of an access path because each record must be 
    compared to see if it meets the select/omit values.
 
   Record length.  A large record length will slow the rebuilding of an 
    access path because more data is looked at.
 
   Storage device containing the data.  The relative speed of the 
    storage device containing the actual data and the device where 
    the access path is stored has an effect on the time needed to 
    rebuild an access path.
 
   The order of the records in the file.  The system tries to rebuild an 
    access path so that it can find information quickly when using that 
    access path.  The order of the records in a file has a small affect 
    on how fast the system can build the access path while trying to 
    maintain an efficient access path.
 
 
All of the preceding factors must be considered when estimating the 
amount of time to rebuild an access path.



______________________________ Reply Separator _________________________________
Subject: Logical File Rebuild time 
Author:  <MIDRANGE-L@midrange.com > at INET_WACO
Date:    10/1/98 6:43 PM


Hi all,
     
We're testing our Y2K conversion programs and we're in need of your advice.
     
We have several hundred physical files comprising almost 50 million records.  Th
routine we go through is to remove all of the logical file members for the targe
physical file libraries, convert the files using a RPG programs, and then we add
ll of the logical file members back to system so that the index paths get 
rebuilt.
     
Because we have access to how far along each RPG program is in the conversion ph
e, we can fairly accurately estimate how long it will take.  We are having diffi
lty determining how long it might take to add the logical file members, however.
     
Is there any programmatic way to gather from the system just how far along an in
x rebuild is?  Even a method for coming up with a rough guess would be great.
     
     
     
Regards,
Rich
     
============================================ 
Rich Duzenbury
http://rich.dyn.ml.org
http://vpsolutions.com
============================================
     
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