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Forum:
Visual FoxPro
Category:
Other
Title:
Miscellaneous
Thread ID:
00202165
Message ID:
00205192
Views:
42
Ed,

Good tip! But there was only one problem, the SYS(3050) will set the amount of memory for VFP's internal disk buffers, but will not limit the amount it allocates.

I spent a little time about a year ago analyzing how VFP uses memory. Here is a fun experiment (although I'm sure Bill Nye could do better)

1) Launch system monitor and monitor Allocated Memory
2) set SYS(3050,1,1024) and SYS(3050,2,1024) - only 1K, as if, right?!
3) Run a select statement on a 10MB+ table with a ORDER BY clause

Notice that at 99% (that is when VFP sorts and writes to disk), that VFP will start grabbing as much memory from the system as it needs to complete the sort.
The bigger the table, the more memory it grabs until the swap file is exhausted, in which case you'll get alot of thrashing and eventually an 'Out of Memory' error. Not to mention some nasty NT messages about virtual memory if your running NT
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