Microsoft KB Archive/184063

= Available Bytes Counter Definition is Incorrect in Perfmon =

Article ID: 184063

Article Last Modified on 10/31/2006

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APPLIES TO


 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition

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This article was previously published under Q184063



SUMMARY
The counter definition in Performance Monitor for the object Memory and counter Available Bytes incorrectly states that:

Available Bytes displays the size of the virtual memory currently on the

Zeroed, Free, and Standby lists. Zeroed and Free memory is ready for

use, with Zeroed memory cleared to zeros. Standby memory is memory

removed from a process's Working Set but still available. Notice that

this is an instantaneous count, not an average over the time interval.

The counter definition should read as follows:

Available Bytes is the amount of physical memory available to processes

running on the computer, in bytes. It is calculated by summing space on

the Zeroed, Free, and Standby memory lists. Free memory is ready for

use; Zeroed memory is pages of memory filled with zeros to prevent later

processes from seeing data used by a previous process. Standby memory is

memory removed from a process's working set (its physical memory) on

route to disk, but is still available to be recalled.

This information can be found in the Counters.hlp file, part of the Windows NT Workstation 4.0 Resource Kit.



MORE INFORMATION
Available Bytes is correctly defined as Physical Memory in the following documents:

Windows NT Workstation 4.0 Resource Kit: Part III, Chapter 12, Page 400

Available Bytes:

Description: How much memory is left for processes to allocate? This is

an instantaneous count, not an average.

The Optimization and Tuning of Windows NT white paper by Scott B. Suhy:

The counter "Memory Available Bytes" displays the amount of free

physical memory. If this counter stays consistently below 4 MB, paging

is occurring and performance is less than optimal.

Additional query words: help mem perf-mon

Keywords: kbbug kbinfo kbpending KB184063

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