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Re: ALTER TABLE (schema migration)

From: no spam <no_at_spam.com>
Date: Wed, 17 Nov 1999 18:54:57 GMT
Message-ID: <5SCY3.32492$m4.112024499@news.magma.ca>


Oracle allows very limited modification of a tables schema. ie no deleteing a column

    modification of type of a column is allowed only if all values in the column are null

The alter table command is for altering storage paramerters etc

The usual way to modify a table schema is to create a new table with nologging and transfer the data from the old table then alter the table to enable logging you will .To keep tables names the same create second table same as first, transfer data, recreate modified original table and transfer data back in.

Paul Gladden wrote in message <80uqgq$mpp_at_nntpb.cb.lucent.com>...
>We're moving to Oracle and I cannot find any information
>relating to Oracle's locking hierarchy for an "alter table"
>or how Oracle's "alter table" is facilitated.
>
>I need to know how the "alter table" occurs, whether the
>table is modified "in-place" or whether Oracle makes
>a table "copy" based on the schema change (add column, drop column, modify
>column) and then drops the source
>table.
>
>What are the conditions which trigger a "copy" migration? How can I detect
>these conditions so I can schedule them?
>
>Maybe Oracle migrates everything "in-place"....
>
>I'm trying to avoid a lengthy table level lock to a
>production system.
>
>Thanks in advance for any replies or pointers where I
>can locate this information.
>
>--
>paul gladden
>pgladden_at_lucent.com
>(303) 538-3805
>
>
Received on Wed Nov 17 1999 - 12:54:57 CST

Original text of this message

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