Black Box 4/BlackBox.cdr/progc/c_all592.arj/TI1004.ASC

Text File | 1992-04-29 | 2KB | 67 lines

  PRODUCT  :  Paradox Engine                        NUMBER  :  1004
  VERSION  :  All
       OS  :  All
     DATE  :  April 29, 1992                           PAGE  :  1/1

    TITLE  :  Packing a Database




  When the Paradox Engine deletes records out of a table, it
  doesn't resize the file; it simply marks the space of the record
  as available.  Thus, as you add records, over time you get a
  bigger data file.  Once you've deleted some records you can pack
  them by either of two methods.

  The first is to use PXTblCopy(), which will copy only non-deleted
  records to a new table.  Rename the old table and name the new
  table with the old table name.  You can delete the old table,
  which you renamed, if there were no errors.

  The second strategy is to use a PXCopyTableStruct() type of
  function to make a new database (without a primary index), and
  then add records from the original table from the bottom up.
  Then, index the new table.  The important point is to first add
  the records to the new table and then add the primary index to
  the new table.  This will insure that as little as possible space
  is used by the data being written to the new table.

  Note that packing a database followed by adding records (when the
  table has a primary index) requires a significant amount of table
  reorganization when records are inserted into the table.  An
  unpacked table will still have room for table additions without
  table reorganization.  Thus, if you are still frequently adding
  records to a table, you may choose to not pack the table.
  Packing a table is normally only useful for tables that are not
  being changed regularly.