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Improved Append Mode Algorithm for Database Data File INSERT

IP.com Disclosure Number: IPCOM000109723D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Adair, JG: AUTHOR [+2]

Abstract

The performance of the INSERT operation on a table is an important aspect of any Database System. Insert performance can be greatly improved by increasing the number of records simply appended to the end of the file without first performing a free space search. However, this append mode usage conflicts with another important goal, that of consuming free space in order to minimize disk space usage. This disclosure provides an algorithm that maximizes append mode usage while efficiently consuming available free space.

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Improved Append Mode Algorithm for Database Data File INSERT

       The performance of the INSERT operation on a table is an
important aspect of any Database System. Insert performance can be
greatly improved by increasing the number of records simply appended
to the end of the file without first performing a free space search.
However, this append mode usage conflicts with another important
goal, that of consuming free space in order to minimize disk space
usage.  This disclosure provides an algorithm that maximizes append
mode usage while efficiently consuming available free space.

      Insert performance can be greatly improved by increasing the
number of records appended to the end of the file without first
performing a free space search, thus avoiding the extra I/O
associated with such searches.  Of course, one cannot avoid free
space searches altogether as minimizing disk space usage is
important.  A way of handling this dilemma is to abide by the rule:
if we know the existing free space will not contain the soon to be
inserted record, append it.

      This was recognized in the first release of OS/2* Database
Manager and the following algorithm was used to support append mode.
If, when a table control block was allocated, it was determined that
the table contained no data records (i.e., table was empty), all
subsequent insert records were appended, until an update or delete
statement was processed.  After that point, free space searches were
performed for each insert.  This means that the only time append mode
was used was when the table contained no free space at all.

      A more efficient algorithm is provided by this disclosure as
follows.  When a table is first...