Change to hot patching

The Microsoft® Windows® operating systems and Microsoft business solutions constitute an environment of choice for many large enterprise customers. For such critical systems, these customers demand high availability and assume the industry standard of "five nines" (99.999%) reliability.

It is important to avoid service interruptions when installing updates on the operating system of such critical systems. Hotpatching provides a mechanism to:
• Update system files without rebooting.
• Update system files without stopping services and processes.

Microsoft reboot reduction initiative

Hotpatching is part of the Microsoft reboot reduction initiative, which seeks to help minimize the need for a full system reboot after installing updates. Reducing reboots is important because IT departments in many organizations implement a time-consuming test cycle every time an update is installed and the system is rebooted. This results in loss of productivity and revenue to the organization until their system is fully verified and operational. Hotpatching allows customers to deploy important updates and patches in a timely, transparent manner without requiring a full system shutdown and restart. This reduces their rollout time.

The following examples demonstrate possible savings from reboot reduction:
• Of the 22 updates that shipped for Windows Server 2003 RTM between April 2005 and August 2005, 15 of them required a reboot. Eight of these could have been hotpatched. This would have reduced the number of reboots by 53%.
• Of the 14 updates that shipped for Windows Server 2003 Service Pack 1 (SP1) prior to August 2005, ten of them required a reboot. Four of these could have been hotpatched. This would have reduced the number of reboots by 40%.

Hotpatch Package Structure

A hotpatch package contains hotpatch and coldpatch binary files for the operating system update.
• The hotpatch binary file contains only the function necessary to address the critical operating system flaw.
• The coldpatch contains the old binary file with the fixed function appended to it and an instruction to jump from the flawed function to the fixed function. Redirecting to the new function ensures that the defective processes in memory are fixed by patching the old function.

Limitations and Compatibility Issues

There are limitations to hotpatching technology, and because of these limitations, not all updates can be hotpatched. Hotpatching does not support components or applications that contain:
• Additions or changes to exports
• Data structure changes
• Dependency changes
• Global state changes
• Infinite loops and persistent stack frames
• Inline assembly code

Package Installation

You can download hotpatch packages from the Microsoft Download Center (http://go.microsoft.com/fwlink/?LinkID=19831). The Software Update Installation Wizard will step you through the hotpatch installation process.

Hotpatch installation for non-Microsoft deployment tools (such as IBM Tivoli and Altiris Patch Management) is supported by enabling hotpatching from the command line. To enable hotpatching from the command line, type:

WindowsServer2003-KB######-x86-LLL.exe /hotpatch:enable

If the hotpatch installation is successful, a reboot will not be required. A log file is created as a part of the installation process, and it will show if the hotpatch installation was successful.