On-Net Surveillance Systems, Inc.
NetDVMS 6.5f User Manual
3 GB Switching
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3 GB Switching
Microsoft Windows 32-bit operating systems can address 4 GB of virtual memory. The operating
system kernel reserves 2 GB for itself, and each individual running process is allowed to address
another 2 GB. This is Windows’ default setting, and for the vast majority of NetDVMS installations it
works fine.
Since the release of NetDVMS version 6.5d , the main components of the server—the Recording
Server service and the Image Server service—have been compiled with the LARGEADDRESSAWARE
flag. This means you can optimize the memory usage of NetDVMS’s Recording Server and Image
Server services by configuring your 32-bit Windows operating system so that it restricts the kernel to
1GB of memory, leaving 3GB of address space for processes compiled with the LARGE-
ADDRESSAWARE flag.
This should improve the stability of especially the Recording Server service by allowing it to exceed
the previous 2 GB virtual memory limit, making it possible for it to use up to 3 GB of memory. The
change in Windows configuration is known as 3 GB switching.
When Is 3 GB Switching Relevant?
For very large NetDVMS installations and/or for installations with many megapixel cameras it can be
relevant to change Windows’ settings so that only 1 GB of virtual memory is reserved for the
operating system kernel, leaving 3 GB for running processes.
If using Windows’ default setting, with only 2 GB virtual memory reserved for running processes, it
has been seen that the Recording Server service in very large installations of NetDVMS may:
•
Behave erratically if getting very close to the 2 GB virtual memory limit. Symptoms can
include database corruption, and client-server or camera-server communication errors.
•
Become unstable and crash if exceeding the 2 GB virtual memory limit,. During such crashes,
the code managing the surveillance system databases is not closed properly, and databases
will become corrupt. In case of a crash, Windows will normally restart the Recording Server
service. However, when the Recording Server service is restarted, one of its first tasks will be
to repair the databases. The database repair process can in some cases take several hours,
depending on the amount of data in the corrupted databases.
If you experience such problems, and you run NetDVMS 6.5d or newer, making Windows use 3 GB for
running processes is likely to solve the problems.
If you have not experienced such problems, but you run NetDVMS 6.5d or newer and your NetDVMS
installation is very large and/or features many megapixel cameras, 3 GB switching is likely to help
prevent the problems from occurring.
The way to configure 32-bit Windows to be LARGEADDRESSAWARE depends on your type of Windows
operating system. In the following, you will see to methods outlining Microsoft's recommended
procedure for increasing the per-process memory limit to 3 GB. Use the first method if running
Windows XP Professional or Windows Server 2003. Use the second method if running Windows 2008
Server, Windows Vista Business, Windows Vista Enterprise or Windows Vista Ultimate.
