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Span Allocation Strategy

IP.com Disclosure Number: IPCOM000110130D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Buquoi, GH: AUTHOR [+4]

Abstract

A method is described for distributing data across spanned table objects.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 59% of the total text.

Span Allocation Strategy

       A method is described for distributing data across
spanned table objects.

      When the Span Utility is used to span a table object, the data
is distributed across the table object files using a round-robin
allocation method.  For data files (.DAT) and index files (.INX) the
allocation size is 1 page (or 4K).  For long field files (.LF) the
size is 32K (this is the size of a single buddy space).  Data is
retrieved from .DAT and .INX files 1 4K page at a time.  Data from
.LF files is retrieved up to 32K bytes at a time.

      Suppose the original data for table "A" is contained in 1 file
in the main database subdirectory and it is spanned into 3 different
paths.  Page 0 (page numbers are 0 oriented) are stored in the 1st
new file path, page 1 is stored in the 2nd, page 2 in the 3rd,
and page 4 back in the 1st file path until all pages have been moved.
                         Before Span:
        C:\SQL00001\SQL00002.DAT contains:  Page 0
                                            Page 1
                                            Page 2
                                            Page 3
                                            Page 4
         After Spanning SQL00002.DAT to 3 new paths:
        C:\NEWDIR...