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Q180171: PRB: FoxPro/Mac Table Operations Do Not Release Memory

Article: Q180171
Product(s): Microsoft FoxPro
Version(s): MACINTOSH:2.6a,3.0b
Operating System(s): 
Keyword(s): kbHWMAC kbvfp
Last Modified: 11-DEC-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Macintosh, version 3.0b 
- Microsoft FoxPro for Macintosh, version 2.6a 
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SYMPTOMS
========

User object memory in FoxPro increases greatly and does not decrease when you
issue any of the following commands on a large table:

     DELETE ALL
     RECALL ALL
     INDEX ON
     SCAN...ENDSCAN

RESOLUTION
==========

Closing and reopening the table reduces memory usage back to its approximate
original value.

STATUS
======

Microsoft is researching this problem and will post new information here in the
Microsoft Knowledge Base as it becomes available.

MORE INFORMATION
================

User object memory is defined as memory used by objects that the user or
programmer defines. User-defined objects include user-defined windows, menu
bars, menus, variables, arrays, open tables, files opened with low-level file
functions, and so on. User object memory can be checked with the SYS(1016)
function.

Applications on the Macintosh obtain memory from the operating system in a
different way than Windows applications. On the Macintosh, the amount of memory
to be allocated to a program is specified in the Get Info window under the Mac's
File menu. The minimum amount of memory to be used for an application and the
preferred amount can be set. However, the application must be closed to change
these settings. If there is enough memory for the preferred amount to be used,
the application takes this much memory from the operating system upon startup
although the application may not be using all that memory. The memory is just
reserved for the application.

In addition to using the SYS(1016) function, the amount of memory allocated to
FoxPro that is in use can be viewed from the About This Computer (or About This
Macintosh, depending on the System software version) command on the Apple menu
in Finder. This dialog box displays the System software version, the amount of
total memory, the amount of virtual memory and the memory allocated to all
running applications, including Finder itself. If Balloon Help is turned on and
the mouse pointer is placed over the memory bar for an application, the balloon
displays the amount of memory in use by the application. For instance, with
Visual FoxPro, the balloon may display "This program is currently using 2.8 MB
out of the 5.9 MB reserved for it."

Steps to Reproduce Behavior
---------------------------

1. Obtain or create a large table. The program below can be used to create a
  large table with 90,000 records. This may take considerable time to run
  depending on the speed of the Macintosh.

        CREATE TABLE BigTable (CharVal C(12), NumVal N(8.0))
        USE BigTable.DBF
        FOR x = 1 TO 90000
        INSERT INTO bigtable (CharVal, NumVal) ;
           VALUES (SYS(2015), RECCOUNT()+1)
        NEXT
        USE

2. Check user object memory with the SYS(1016) function. From the Command window
  type in the code below and then press ENTER:

        ? SYS(1016)

  A number should appear on the FoxPro screen.

  Here is an example:

  2516480

3. In the Command window type:

        USE Big_Table
        ? SYS(1016)

  The User object memory should increase slightly.

4. Issue a DELETE ALL command in the Command window and check SYS(1016) again.

5. Now issue a RECALL ALL in the Command window and check SYS(1016).

6. Close the table by issuing just the USE command in the Command window and
  check SYS(1016).

7. Similar results can be seen using the INDEX ON command and a SCAN...ENDSCAN
  loop. The INDEX ON <fieldname> TO <filename.idx> command uses
  more memory than the DELETE ALL or RECALL ALL commands.

REFERENCES
==========

For more information on creating large tables for testing purposes, please see
the following article in the Microsoft Knowledge Base:

  Q170128 HOWTO: Programmatically Create Large Tables for Testing Purposes

Additional query words:

======================================================================
Keywords          : kbHWMAC kbvfp 
Technology        : kbHWMAC kbOSMAC kbVFPsearch kbAudDeveloper kbFoxproSearch kbFoxPro260aMac kbVFP300bMac
Version           : MACINTOSH:2.6a,3.0b
Issue type        : kbprb

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