Re: ASSM tablespace three level bmp block questions.

From: lsllcm <>
Date: Thu, 2 Apr 2009 18:23:13 -0700 (PDT)
Message-ID: <>

On Apr 1, 10:52 pm, Michael Austin <> wrote:
> lsllcmwrote:
> >> Here is a good start...
> >> quoted text -
> >> - Show quoted text -
> > Hi Michael,
> > Thanks for the document, but I still cannot find the answer from the
> > document
> > Thanks
> > Jacky
> The last thing I have seen on this level of information is: "Oracle does
> not publish the internals of space management" - This was one of the
> "features" Oracle obtained when they purchased the DEC/Rdb product. IIRC
> there was a particular patent that is used to make all of this work. If
> you can find some of the old DEC/Rdb internals manuals, you may get a
> better idea of how this works. In Rdb, you could actually set the SPAM
> interval.  There are Area Inventory pages (AIP), "Area" bitmaps (aka
> tablespace bitmaps aka ABM) and SPAce Management bitmaps) and Data
> pages. A data page was 1-to-n multiple of the disk block size.  So, in
> VMS all data on disks were stored in 512byte blocks.  A "page size"
> (configurable) of 1024 was 2 disk blocks. The SPAM interval (in Rdb) was
> the number of data_pages per SPAM page. On disk if the DATA:SPAM was
> 100, you would have a SPAM page followed contiguously as possible by 100
> data pages of size 1024bytes. The ability to size these very small was
> to reduce high volume insert contention. In the Oracle/RDBMS
> implementation a data page is know as an extent (they didn't want to
> confuse the masses with new terminology.)  They also seemed have changed
> the terminology of the SPAM "threshold" (fullness value) and when it
> should "consider" adding more data to this page (pctfree/used concept).
> One other note, there are some additional differences and possibly new
> concepts (as stated, none of this is actually published out side of
> Oracle) in the current ASSM implementatin but this is what happens when
> the best minds in the database engine arena get together.

Thanks, I need some time to understand it Received on Thu Apr 02 2009 - 20:23:13 CDT

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