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From the manual (Admin Guide, chapter 38)

Rowid in Fragmented Tables

Unlike rows in a nonfragmented table, the database server does not
assign a
rowid to rows in fragmented tables. If you wish to access data by rowid,
you
must explicitly create a rowid column as described in the Performance
Guide
for Informix Dynamic Server. If user applications attempt to reference a
rowid
in a fragmented table that does not contain a rowid that you explicitly
created, the database server returns an appropriate error code to the
application.

Accessing Data Using Rowid in Fragmented Tables

From the viewpoint of an application, the functionality of a rowid
column in
a fragmented table is identical to the rowid of a nonfragmented table.
However, unlike the rowid of a nonfragmented table, the database server
uses an index to map the rowid to a physical location.

When the database server accesses a row in a fragmented table using the
rowid column, it uses this index to look up the physical address of the
row
before it attempts to access the row. For a nonfragmented table, the
database
server uses direct physical access without having to do an index lookup.
As
a consequence, accessing a row in a fragmented table using rowid takes
slightly longer than accessing a row using rowid in a nonfragmented
table.

You should also expect a small performance impact on the processing of
inserts and deletes due to the cost of maintaining the rowid index for
fragmented tables.



From the Performance Guide:

In a fragmented table, the row ID is no longer a unique nonchanging
pointer to the row on a disk. The database serve now uses the
combination
of fragment ID and rowID internally, inside an index, to point
to the row. These two fields are unique but can change over the life
of the row. An application cannot access the fragment ID; therefore,
Informix recommends that you use primary keys to access a specific
row in a fragmented table. For more information, refer to the Informix
Guide to Database Design and Implementation.





-----Original Message-----
From: owner-informix-list@iiug.org [mailtowner-informix-list@iiug.org]
On Behalf Of Colin Dawson
Sent: 31 August 2005 05:56 AM
To: informix-list@iiug.org
Subject: Re: ROWID functionality

Unless you use the WITH ROWIDS clause when creating the fragmented
table.....



Regards

Colin

There are 10 types of people in the world, those that understand binary
and
those that don't





>From: david@smooth1.co.uk
>Reply-To: david@smooth1.co.uk
>To: informix-list@iiug.org
>Subject: Re: ROWID functionality
>Date: 30 Aug 2005 12:19:34 -0700
>
>rowid is not unique for fragmented tables.
>
>but then maybe the logical log record will include the fragment id for
>fragmented tables?
sending to informix-list
sending to informix-list