AW: convert dds to ddl

["Birgitta Hauser" <Hauser@xxxxxxxxxxxxxxx>]

Hi,

depending on the release you are, you may replace all DDS described logical
files (except join logical files) with SQL indexes.
An SQL index can be used with native I/O like any other keyed logical file.

With release 6.1 derived and sparse indexes are introduced, that means it is
now possible to select fields/columns within an index, create new columns
and specify them as key and even add where clauses (that will replace
select/omit clauses).

In former releases there was a recommendation to create indexes first and
after DDS described logical files.
A DDS described logical file has per default a page size for 8K while an SQL
index has a default page size of 64k.
In this way a DDS described logical file can share access path with an SQL
index (and gets the larger page size inherited) but not vice versa.
An SQL index will only share access path with an SQL index (or a DDS
described logical file) with at least the same page size and where the key
fields an exact match.

To avoid too much access path (which must be actualized with each insert,
update or delete on the based physical file/table), access paths should be
shared as much as possible.

Mit freundlichen Grüßen / Best regards

Birgitta Hauser

"Shoot for the moon, even if you miss, you'll land among the stars." (Les
Brown)
"If you think education is expensive, try ignorance." (Derek Bok)
"What is worse than training your staff and losing them? Not training them
and keeping them!"

-----Ursprüngliche Nachricht-----
Von: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] Im Auftrag von rob@xxxxxxxxx
Gesendet: Friday, 06. August 2010 18:49
An: Midrange Systems Technical Discussion
Betreff: Re: convert dds to ddl

Not sure about this:
<snip>
I will create new SQL indexes prior to re-creating my old logicals.
what else can/should I do to my logicals?
</snip>
Were you thinking about recreating your logicals in DDS, but first create 
indexes?  I do not see a reason to use DDS to recreate your logicals.

Some indexes you may not have but which may come in handy ...
If you have select/omit logicals (which you can do just fine in DDS on 
6.1) like this
CREATE INDEX ROB/gqcyl1
ON ROB/GQCY 
(MUVALUE) 
WHERE RECID='A' 

Then you may also want an index like this first
CREATE INDEX ROB/gqcyl2
ON ROB/GQCY 
(recid, MUVALUE) 

I think this will help performance of queries over the base table which do 
something like
SELECT ...
FROM GQCY
WHERE RECID='A'...
And I think you want those created first.


Rob Berendt