At 03:35 PM 5/7/97 -0500, Larry Boyd wrote:
>What you want to do is enable the database for CIU (Critical Item Update)
>and then DBUPDATE The record, instead of DBDELETE/DBPUT. This will allow
>the record to retain its current position. The second issue in your
>message has to do with the sort/key retrieval. If you DBDELETE/DBPUT a
>record with "key1" sorted on "sort1", then a chained read of "key1" should
>have the record as the last record with the matching "sort1" value. For
>example, if the key1 value is 12345 and the sort1 value is ABC, then the
>record you add will show up as the last 12345ABC record, assuming that
>there are multiple 12345ABC records. If you search and read from 'key2',
>which does not have 'sort1' defined on it, then the record will show up as
>the last record in the chain (even if the physical location of the record
>is exactly the same). This is because IMAGE adds the records in
>chronological order and the "new" record is last.
By using CIU, only the position of the entry in the key field being changed
will be affected. For example, a dataset has search fields KEY1 and KEY2
with no sort fields. Each search key for a particular entry has a chain
length of 6 entries and this particular entry is the 3rd entry in both
chains. If CIU is used to change the value of KEY1, the entry will be
placed at the end of the chain for the new value of KEY1. However, the
entry will remain as the 3rd entry for the KEY2 chain. On the other hand,
if DBDELETE/DBPUT are used, after changing the value of KEY1, the entry
would now be in the 6th position on KEY2.
CIU will help retain entry chronology for unaffected search keys.
Furthermore, the performance analysis which Wirt Atmar and I did, and which
I presented at the New Orleans conference, showed that CIU can provide
upwards to 800% better performance in changing a single search field value
on a 16-key dataset. If any of the key fields which are not being changed
have sort fields, using CIU saves even more overhead as there is no sort
field search to re-insert the entry like there would be if DBDELETE/DBPUT
are used.
/jf
_\\///_
(' o-o ')
___________________________ooOo_( )_OOoo____________________________________
Jerry Fochtman, Director Voice: 713/621-2808
HP3000 Research & Development 800/621-2808
Bradmark, Inc. Fax: 713/621-1639
4265 San Felipe, Suite 800 mailto:[log in to unmask]
Houston, TX 77027 http://www.bradmark.com
"Choose a job you love, and you will never have to work a day in your Life."
--- Confucius
___________________________________Oooo_____________________________________
oooO ( )
( ) ) /
\ ( (_/
\_)
|
