As in all Unix-based systems, Mac OS X assigns specific access privileges, known as permissions, to each of your programs, folders, and documents, which are associated with a particular owner, a group, or groups. When an error in your permissions settings occurs, it may cause significant problems. For example, your applications may not launch or your system may respond sluggishly. These problems are more likely to occur after you update your operating system or install new software.
There is some debate over how often you should repair your disk permissions, but we do it once a month or after OS X updates.
To improve your system’s performance, use the repair disk permissions function in OS X’s Disk Utility program:
1. To open Disk Utility, from your Applications folder, open your Utilities folder and double-click the Disk Utility icon.
2. In the column on the left, click your Startup disk’s icon.
3. Click the First Aid tab, and then click Repair Disk Permissions. Disk Utility will reset any files and folders with incorrect settings.