Impact of removing columns in a table

Hello

Using oracle 11.2.0.3

We want to remove some columns in a table in a tidy exercise - as they are not necessary - the application code that references will change them.

Anyone see any negative impact: what are non indexed columns cannot therefore predict problems - just thought I would check in the case where someone met all similar questions making.

Thank you

Anyone see any negative impact: what are non indexed columns cannot therefore predict problems - just thought I would check in the case where someone met all similar questions making.

Yes - there MAY BE negative effects.

1. you can lose data if you do not have this table saved (or active flashback) so you can restore the data and move the original table if there is a problem during the operation. There is ALWAYS a risk of system failure even if the risk is low. Abandoned data cannot be recovered, so you better have a backup from top - to the second.

2. the DROP operation actually deletes the data for EACH ROW in the table. This means a full table scan and possible restructuring of blocks. These columns can be part of, or severely, chained the lines. They could be the LOB columns whose data is stored in another segment that must also be cleaned.

You have not displayed enough details for us to know what would be the issues here for your unknown column types.

But exercise alone.

http://docs.Oracle.com/CD/B28359_01/server.111/b28310/tables006.htm#i1006709

Deleting table columns

When you issue a ALTER TABLE...DROP COLUMN statement, the column descriptor and data associated with the target column are removed from each row in the table. You can drop multiple columns with a single statement.

At a minimum, you need to back up this table before and after the MOVE. This backup operation will use the resources so it can also have an impact.

Tags: Database

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