RE: Replacing a view with selects on it
- From: "Justin Cave (DDBC)" <jcave@xxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Sun, 16 May 2004 10:09:35 -0600
My preference in this sort of environment would be to replace the data
in a single transaction, making sure that I had allocated enough UNDO to
satisfy any long-running queries. This might mean that the load was a
single transaction into a single copy of the tables, it might mean that
the load populates a series of staging tables in a number of
transactions and there is a single transaction that MERGEs these staging
tables into the main tables.
Justin Cave
Distributed Database Consulting, Inc.
http://www.ddbcinc.com/askDDBC
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of jaromir nemec
Sent: Sunday, May 16, 2004 9:50 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: Replacing a view with selects on it
H,
=20
There is a common strategy in some DSS systems to refresh the data by
replacing the access views (they are repointed to the new version of
data). In case there is defined a loading window (with no access) I
guess this approach is very safe. But what about a 24*7 environment, if
there is no "midnight" to do the replace.
Is it acceptable to simple replace a view if there could be some session
reading it?=20
=20
I performed some simple test:
=20
1) start long select from a view
2) create or replace the view while the session is running
3) see what happen:)
The reader session did "survived" (I guess with the cached version of
the view).
But it is no prove!=20
Are there situation, where this approach can cause problems? Any
experience with this topic on the list?
=20
Thanks
=20
Jaromir D.B. Nemec
http://www.db-nemec.com
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