BTSCANNER ALICE mode
Hello all, Is anyone aware of any documentation, beyond the release notes, on just exactly what the ALICE mode for BTSCANNERS is/does? I know it stands for Adaptive Linear Index Cleaning Engine, or something similar, but not much beyond that. Is there any good documentation out there? Thanks, - TJG
On Jan 27, 11:15 am, "Thomas J. Girsch" <tgir...@NOSPAM.gmail.com> wrote: > Hello all, > > Is anyone aware of any documentation, beyond the release notes, on just > exactly what the ALICE mode for BTSCANNERS is/does? I know it stands > for Adaptive Linear Index Cleaning Engine, or something similar, but not > much beyond that. Is there any good documentation out there? > > Thanks, > > - TJG I don't know if there is any documentation, but there have been some presentations written about it. Basically it's a 3rd method that the BTScanner can use to figure out which index pages that need to be cleaned. ALICE mode breaks the entire index up into regions (a region can be thought of as just a set of logically contiguous page blocks) and then uses a bit map to mark which regions need to be cleaned. Additionally, as it attempts to clean a region, if it determines that it read a lot of pages in that region which didn't need to be cleaned, it will decide that, that region size defines too many pages, so it will then double the size of your bitmap and half the number of pages in a region. I don't recall the exact starting size of a region (in number of pages) or the exact point in how many pages in a region need to not be cleaned for it change the size of the bit map and region, but that's the general idea on how it works. Only other thing would be, is the regions get marked to be cleaned as a row in that is deleted/updated. The BTScanner builds it's hot list the same, but when an ALICE mode index is cleaned, the BTScanner only needs to consult the bitmap to determine which regions need to be scanned for pages that require cleaning. Jacques
if you understand German: http://www.informix-zone.com/informix-german-newsletter check out Ausgabe September 2007. GOOD STUFF See you Superboer. way fast=http://www.clipjes.nl/clip/nederlands/n/normaal_- _oerend_hard.html On 27 jan, 22:05, jpren...@yahoo.com wrote: > On Jan 27, 11:15 am, "Thomas J. Girsch" <tgir...@NOSPAM.gmail.com> > wrote: > > > Hello all, > > > Is anyone aware of any documentation, beyond the release notes, on just > > exactly what the ALICE mode for BTSCANNERS is/does? I know it stands > > for Adaptive Linear Index Cleaning Engine, or something similar, but not > > much beyond that. Is there any good documentation out there? > > > Thanks, > > > - TJG > > I don't know if there is any documentation, but there have been some > presentations written about it. Basically it's a 3rd method that the > BTScanner can use to figure out which index pages that need to be > cleaned. ALICE mode breaks the entire index up into regions (a region > can be thought of as just a set of logically contiguous page blocks) > and then uses a bit map to mark which regions need to be cleaned. > Additionally, as it attempts to clean a region, if it determines that > it read a lot of pages in that region which didn't need to be cleaned, > it will decide that, that region size defines too many pages, so it > will then double the size of your bitmap and half the number of pages > in a region. I don't recall the exact starting size of a region (in > number of pages) or the exact point in how many pages in a region need > to not be cleaned for it change the size of the bit map and region, > but that's the general idea on how it works. Only other thing would > be, is the regions get marked to be cleaned as a row in that is > deleted/updated. The BTScanner builds it's hot list the same, but > when an ALICE mode index is cleaned, the BTScanner only needs to > consult the bitmap to determine which regions need to be scanned for > pages that require cleaning. > > Jacques