Re: Ingres to Oracle Conversion

In <3248777f.44317319_at_news.concentric.net>, jljoslin_at_concentric.net (J L Joslin) writes:
>On 24 Sep 1996 15:26:37 GMT, Liam_McCauley_at_QSP.co.uk@ (Liam
>McCauley) wrote:
>
>>In <32482944.3FC_at_rrds.co.uk>, Ron Ekins <R.Ekins_at_rrds.co.uk> writes:
>>>Has anyone any experience in moving a large Ingres database to Oracle ?
>>>The Ingres database is mainly compressed BTREE tables, will this therefor
>>
>>
>>Ingres only compresses integer, float, date & money fields if they contain
>>a null value. Varchars (& chars, I think) are only "compressed" in that the
>>full length of the field is not stored.
>>i.e. a varchar(200) not null field with a row containing "XYZ" will be stored in
>>3 bytes (+1? for the length) if the table is compressed, rather than 200 (+1)
>>if not compressed.
>>
>>As far as I'm aware, Oracle's varchar2 behaves like Ingres varchar on a
>>compressed table, so space should not be a problem.
>>
>
>
>Actually, Liam, Ingres runs all data through a compression algorithm
>when it's inbound and decompression outbound. Very similar to the way
>PKZIP/UNZIP do their thing. So an equivalent Oracle table will require
>a bit more space than it's compressed Ingres counterpart. Unless they
>are using 7.3 bitmapped indexes, their indexes will definitely take
>more space.
>

Ingres version 6 behaves as I have described. This comes from the documentation (DBA Guide IIRC), and I have verified it myself. OpenIngres may be different (although I am doubtful - the documentation gives no indication). I have not had the opportunity to check it.

Cheers,
Liam

-- 

    Liam McCauley                Email: Liam_McCauley_at_QSP.co.uk
    Database Administrator       Tel  : (0191)402 3283
    Quality Software Products
    Gateshead
    UK                             Views expressed are my own