Re: rollback segment question

The rollback segments record the changes required to bring a block back to the state it was in before it was changed. When you insert data, you are changing blocks, even if it is just from being empty to having data. If you had to roll back, you would have to bring that block back to the way it looked before you made any changes. Any other users who start a query before you commit have to reconstruct blocks in memory to the way they looked before you changed them (consistent read).

Remember that you can insert data into datablocks that already have data in them, as long as the capacity of the block has not yet reached PCTFREE, or has fallen below PCTUSED.

HTH,
--
Jeremiah

Dennis wrote:
>
> A dump file which contains more than 1 GB data was imported into the
> Oracle database. When it was imported, the error message asked me to extend
> the rollback segment size. I did what it said. Everything is OK. But I
> just can't figure out why the Oracle server need more rollback segments when
> I import a dump file (insert new data). Update needs rollback segments to
> store the old value, insert doesn't. Does anyone explain why? Thanks!
Received on Tue Dec 28 1999 - 12:09:00 CST