Re: ASSM tablespace three level bmp block questions.
From: lsllcm <lsllcm_at_gmail.com>
Date: Sun, 12 Apr 2009 06:11:03 -0700 (PDT)
Message-ID: <da187884-216f-4ecd-824a-9985442d6ce7_at_y6g2000prf.googlegroups.com>
On Apr 11, 11:02 pm, "Jonathan Lewis" <jonat..._at_jlcomp.demon.co.uk> wrote:
> "lsllcm" <lsl..._at_gmail.com> wrote in message
>
> news:88e531d4-55df-4e53-abeb-5210021eafe3_at_d25g2000prn.googlegroups.com...
>
> > Hi All
>
> > I have one question about ASSM tablespace. The ASSM tablespace has
> > three level BMP blocks to
> > indicate if block is used. How many blocks does one L1 BMP block
> > manages? After do one test, I found
> > the number increases when the data increases. Is there any rule about
> > it?
>
> > How many L1 BMP blocks does one L2 BMP block manages. After do the
> > test, I found the number 241 when
> > the blocksize is 2048 bytes. Is that right?
>
> > Any answers are appreciated.
>
> I don't think there is any public documentation of such things, and
> given the apparent flexibility of the algorithms I don't think you can
> expect a solid answer.
>
> Your 241 L1's per L2 in a 2KB block looks about right since an L1
> reference seems to be 8 bytes when you dump an L2,
>
> The number of blocks referenced by an L1 BMB depends on the extent
> sizes and the block sizes - larger extents lead to more blocks more L1 BMB,
> for example I have a 64MB extent size with an 8KB block that gives 256
> blocks
> per L1 BMP. An entry in an L1 block needs only 4 bits - so an single L1
> block could reference far more that the 1024 data blocks that Tanel quotes
> in his presentation , but I'd guess that the actual number is restricted to
> avoid
> excessive content on L1 blocks.
>
> --
> Regards
>
> Jonathan Lewishttp://jonathanlewis.wordpress.com
>
> Author: Cost Based Oracle: Fundamentalshttp://www.jlcomp.demon.co.uk/cbo_book/ind_book.html
>
> The Co-operative Oracle Users' FAQhttp://www.jlcomp.demon.co.uk/faq/ind_faq.html
Date: Sun, 12 Apr 2009 06:11:03 -0700 (PDT)
Message-ID: <da187884-216f-4ecd-824a-9985442d6ce7_at_y6g2000prf.googlegroups.com>
On Apr 11, 11:02 pm, "Jonathan Lewis" <jonat..._at_jlcomp.demon.co.uk> wrote:
> "lsllcm" <lsl..._at_gmail.com> wrote in message
>
> news:88e531d4-55df-4e53-abeb-5210021eafe3_at_d25g2000prn.googlegroups.com...
>
> > Hi All
>
> > I have one question about ASSM tablespace. The ASSM tablespace has
> > three level BMP blocks to
> > indicate if block is used. How many blocks does one L1 BMP block
> > manages? After do one test, I found
> > the number increases when the data increases. Is there any rule about
> > it?
>
> > How many L1 BMP blocks does one L2 BMP block manages. After do the
> > test, I found the number 241 when
> > the blocksize is 2048 bytes. Is that right?
>
> > Any answers are appreciated.
>
> I don't think there is any public documentation of such things, and
> given the apparent flexibility of the algorithms I don't think you can
> expect a solid answer.
>
> Your 241 L1's per L2 in a 2KB block looks about right since an L1
> reference seems to be 8 bytes when you dump an L2,
>
> The number of blocks referenced by an L1 BMB depends on the extent
> sizes and the block sizes - larger extents lead to more blocks more L1 BMB,
> for example I have a 64MB extent size with an 8KB block that gives 256
> blocks
> per L1 BMP. An entry in an L1 block needs only 4 bits - so an single L1
> block could reference far more that the 1024 data blocks that Tanel quotes
> in his presentation , but I'd guess that the actual number is restricted to
> avoid
> excessive content on L1 blocks.
>
> --
> Regards
>
> Jonathan Lewishttp://jonathanlewis.wordpress.com
>
> Author: Cost Based Oracle: Fundamentalshttp://www.jlcomp.demon.co.uk/cbo_book/ind_book.html
>
> The Co-operative Oracle Users' FAQhttp://www.jlcomp.demon.co.uk/faq/ind_faq.html
Hi Jonathan,
Thanks for your answer. Received on Sun Apr 12 2009 - 08:11:03 CDT