Which practice is least effective when managing system updates?

Applying all updates immediately without review is least effective when managing system updates because it can lead to disruptions and vulnerabilities. This practice does not allow for adequate assessment of the updates' impact on the existing system. Without a review process, there is a risk that updates may introduce new issues or conflict with existing configurations, leading to system instability or downtime. Effective management of system updates requires a careful evaluation of each update, which includes understanding its benefits, potential risks, and compatibility with current infrastructure. The other practices mentioned—regularly backing up configurations, documenting changes, and testing updates in a controlled environment—are all crucial for ensuring a smooth update process and maintaining system integrity. These practices collectively enable a structured approach to change management, crucial for minimizing adverse effects and ensuring system resilience.