Re: Rollback Segment Question

Oracle will not reuse any rollback extent that still has a single active transaction. Only when the last transaction active in an extent finishes (commit ot rollback) does the extent become available for reuse.

Could they have programmed this on a block by block basis? Sure. Did they? No. Why? Probably more costly.

Jeanne wrote:

> I am currently studying for the 2nd OCP exam (DBA), and I am a little
> confused about what I am reading about rollback segments.
>
> All the examples in the array of books strewn across my desk say that 2
> transactions can share an extent in a rollback segment, but that blocks
> within an extent can only store one transaction.
>
> But then they start talking about the round-robin circular search for new
> extents, and if the "extent" to which they've circled around contains active
> transactions, then it must grab a new extent, because that extent is tied
> up. But I thought that extent was share-able, only individual blocks within
> an extent weren't share-able. I am failing to see how these "blocking
> sessions" arise.
>
> Does anyone see my confusion? Thanks.
Received on Sat Feb 13 1999 - 20:46:59 CST