Memory Resizing and Reallocation

In earlier versions of OS/2, an application could increase or decrease the size of an allocated memory segment by reallocating the segment.

Memory objects cannot be resized. Instead, an application should allocate a sparse memory object of whatever size might be necessary, then commit or decommit portions of the object.

If the amount of memory required cannot be determined at the time the memory is allocated, the application should allocate a sparse memory object large enough to meet the largest memory requirement. The application can then change the amount of committed memory as necessary.

For example, if you anticipate your application will use around 512KB of memory for most purposes, but might use 5MB under certain circumstances, you might take the following steps:

• During program initialization, use DosAllocMem to allocate 5MB.

• Commit the first 512KB (or some part of it) using DosSetMem.

• Proceed with normal processing.

• If extra memory is required occasionally, commit it and decommit it using DosSetMem.

• When the situation arises that the application requires the full 5MB, commit it at that time, using DosSetMem, then decommit it after you are finished with it, also using DosSetMem.

• When the application is finished with the memory, use DosFreeMem to release the memory back to the system.