Re: Data load ideas
- From: "jaromir nemec" <jaromir@xxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 4 May 2004 00:01:50 +0200
----- Original Message -----
From: "Tim Gorman" <tim@xxxxxxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Saturday, May 01, 2004 6:01 PM
Subject: Re: Data load ideas
> Why are you using foreign keys in a data warehouse anyway?
Hi Tim,
I completely agree with you on the topic of constraints, but I guess that
this is not the only problem by exchange partition. What about the "read
side" of this problem?
If there is a loading window in the data warehouse where no selects are
permitted everything is OK. But while refreshing continuously you must take
into account, that there could be some reading transaction at the time of
exchange partition. Can those reading sessions expect the transactional
behaviour (no dirty reads for example) of accessed data?
The problem is, in my opinion, that an exchange partition is a DDL, even
thou used as a substitute for a DML, so the influence on a reading session
could be - theoretically - the same as for example drop and recreate the
table while reading it. It means somewhere between not really predictable
and fatal.
I have experimented little bit with this stuff and saw interesting results
e.g. combining serializable isolation level with exchange partition with
validation, but I'm not completely sure if exchange partition is a legal
publishing mechanism on a DSS without loading window.
In my opinion there are two different tasks implemented using exchange
partition:
* total refresh of a snapshot (exchange old version by a new version of
data)
* maintenance of a rolling window (exchange partition is used add new data
and to remove old data)
Any experience with exchanging partition while selecting the table?
Thanks
Jaromir D.B. Nemec
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