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Very Poor Performance of SQL on Local Table
Message
From
21/02/2002 08:14:08
Walter Meester
HoogkarspelNetherlands
 
General information
Forum:
Visual FoxPro
Category:
Databases,Tables, Views, Indexing and SQL syntax
Miscellaneous
Thread ID:
00618884
Message ID:
00623075
Views:
30
Hi Christof,

>FoxPro's memory management is like a 3-tier application. *g* One layer is responsible for FoxPro code and provides a operating system independent view on memory. This layer implements the page pool memory controlled by SYS(3052) and the handle pool memory that is used for variable, forms, windows, menus, popups, table buffering, etc. FoxPro only uses these memory management functions to allocate memory.

>These memory management functions than talk to a "backend" to perform the actually memory operation. This backend is operating system specific. VFP3/Mac has a different one than VFP/Windows, FPW had yet another one and FPD even several, depending on whether you use the extended or standard version.

>This backend has definitely changed, but the FoxPro internal memory management hasn't.

I can't look into the memory management design, but I recall that FPW 2.x was not able to free unused memory back to the OS. If this function is implemented in the 'back-end' layer then you could be right, however if this is a function that belongs to the internal memory management (I think that both layers have at least something to do with it) then I think this is not entirely true. And how does garbage collection fit into these layers ? A part of the 'backend' layer or both ?

Walter,
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