Visual FoxPro Has 3 New SYS Functions Related to Memory

The information in this article applies to:

• Microsoft Visual FoxPro for Windows, versions 3.0, 5.0, 5.0a

SUMMARY

There are three new SYS functions in Visual FoxPro related to memory.

The new functions are:

• SYS(3050), which sets buffer memory size.
• SYS(3051), which sets lock retry interval.
• SYS(3052), which overrides SET REPROCESS locking.

MORE INFORMATION

SYS(3050) - Set Buffer Memory Size

SYS(3050, nType, nBuffMemSize)

• nType specifies foreground (1) or background (2)
• nBuffMemSize specifies a suggested, maximum amount of buffer memory you want Visual FoxPro to commit in foreground or background mode.

This function should be used in place of the MEMLIMIT command that was placed in the Config.fpw file in previous versions of FoxPro. The MEMLIMIT command is ignored in Visual FoxPro.

To set the foreground or background buffer memory size to 6 and 4 million respectively, create a program and call it from the Config.fpw file. For example, add the following line to call Myprogram.prg from the Config.fpw file. Remember, only one Command= line is allowed in the Config.fpw file.

   COMMAND = DO Myprogram.prg

   =SYS(3050,1,6000000)
   =SYS(3050,2,4000000)

   ? SYS(3050,1)
   ? SYS(3050,2)

SYS(3051) - Set Lock Retry Interval

SYS(3051, nWaitMilliseconds)

• nWaitMilliseconds specifies the suggested interval of time for Visual FoxPro to wait between retries while attempting to lock a record, file, memo, or index. The valid range is from 100 to 1000 milliseconds. Passing a zero for nWaitMilliseconds will cause Visual FoxPro to reset to its startup value which is 333.

SYS(3052) - Honor REPROCESS for Index or Memo Lock Attempts

SYS(3052, nFileType, lHonorReprocess)

• nFileType specifies index (1) or memo (2).
• lHonorReprocess, when equal to .T., specifies that Visual FoxPro should honor the SET REPROCESS setting when Visual FoxPro attempts to lock files. When lHonorReprocess is off (.F.), the locking behavior is to wait indefinitely for locks on the specified files. Honoring SET REPROCESS is recommended if your program is using transactions because reduces the risk of deadlocks. Turning it on for indexes may adversely impact concurrency control because index locks may be held for a longer period of time.

Using SYS(1001) and SYS(1016)

SYS(1001) returns the virtual memory pool size. SYS(1016) returns the amount of memory used by defined objects. However, in order to get accurate memory statistics, you should use Window API functions.