Art S. Kagel wrote:
> DA Morgan wrote:
>
>> Ian wrote:
>>
>>> jdokos wrote:
>>>
>>>> Hello,
>>>> <SNIP>
>>
>>
>> Is it true that in Informix VARCHAR takes more space than CHAR? In
>> Oracle the waste of space and CPU comes with working with CHAR and
>> it has been almost completely abandoned.
>
>
> Yes and no. A VARCHAR stored a 1 byte length and an LVARCHAR a 2 byte
> length as part of the field, however, both types are true variable
> length fields. So, if the field is full it will take a byte or two
> extra storage than the equivalent CHAR, if not full it will take less
> storage than CHAR.
>
> The rub and performance hit for using VARCHAR or LVARCHAR in IDS is
> similar to that in DB2. If expanding a variable column in a row causes
> the row to no longer fit on the data page which is its home then the row
> is moved to another page and a forwarding pointer is left behind in its
> original location. This is so that index keys do not have to be
> rewritten. Beyond that if expanding a variable lenght field on a row
> causes the row to become larger than a page (not possible in DB2, but
> that's another issue) IDS will create a remainder page to hold the tails
> of oversized rows from several pages and a forwarding pointer to the
> location of the tail is left at the end of the home row portion. Since
> LVARCHARs can be as long as 32K this can happen several times with a row
> taking up several full pages and a tail entry.
>
> Usually, performance wise, I find breaking long strings into multiple
> fixed length CHAR rows in a child table or by using a MULTISET is far
> more efficient and no harder to code for.
>
> Art S. Kagel

Thanks.

Daniel Morgan
--
Daniel A. Morgan
http://www.psoug.org
damorgan@x.washington.edu
(replace x with u to respond)