Re: Ingres to Oracle Conversion

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
>>give us a problem with disk space & performance.
>>
>>Regards
>>
>>Ron Ekins
>
>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.
>
>As far as performance goes... lets just say that for, our application, Oracle
>was faster than Ingres. For your application, this may not be the case
>(benchmark, if you get the chance).
>
>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
>

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.

Jim Joslin Received on Wed Sep 25 1996 - 00:00:00 CEST