Here is a document from Bmer from MacOSG who wrote about OnyX's Terminology. I thought that it would be important as reference to put in here (I asked for permission first)
One utility we recommend a lot is OnyX. The following terms are from OnyX's Help menu. These explanations should help you understand what each function does.
Verify and Repair permissions: This option verifies System file permissions on the hard disk and repairs them as necessary. Incorrect permissions can result from certain installers or after a System crash, and might cause unexpected behavior. OnyX restores the permissions of all System files and Apple-installed software.
Daily script: This script (daily) removes scratch and junk files (/tmp, /var/tmp and /var/rwho), backs up the NetInfo database, checks subsystem status, and rotates the System.log file. By default, this script is executed every day at 3:15 AM, if the computer is turned on.
Weekly script: This script (weekly) rebuilds the Locate and Whatis databases, restarts the Syslog process and rotates the ftp.log, ipfw.log, lookupd.log, lpr.log, mail.log, netinfo.log files and access_log and error_log files in the httpd folder. By default, this script is executed every Saturday at 4:30 AM, if the computer is turned on. This operation might take a few minutes; please be patient..
Monthly script: This script (monthly) restarts the syslog daemon, runs login accounting and rotates the wtmp.log and install.log files. By default, this script is executed the first day of every month at 5:30 AM, if the computer is turned on.
Optimize the System: This command allows updating of information in System libraries and executables when new files are added to the System. The -force option forces updating of all files. With the force option, some System settings might be changed, but the contents of the Keychain and the passwords themselves will not be modified. It is recommended that you restart the computer after executing this command.
The optimization of the system uses the update_prebinding command. However, the launching of this operation is not really necessary, because Mac OS X does it as soon as it's necessary, in the background.
Update Locate database: This option allows updating of the Locate database (/private/var/db/locate.database). Locate is a Unix tool that allows searching for files very rapidly. Rather than scanning a disk, it uses a database that indexes all file paths in the System, and returns the results almost instantaneously. Updating the Locate database might take a few minutes.
Update Whatis database: This option allows updating of the Whatis database (/usr/share/man/whatis.db). Whatis is a command whose database facilitates searching for man pages (Unix documentation provided with Mac OS X).
These two databases are also updated when the weekly maintenance script is executed.
Browsers' Cache: This option deletes the files created when loading Internet pages in the Web browser.
Download Cache: This option deletes the files created when files are downloaded from the Web.
Browsers' History: This option deletes the history of pages that Web browsers use to make pages load more quickly.
Cookies: Many Web sites store small files, named 'cookies', on your computer, to make return visits easier, for example, a transaction between you and a commerce site online, to avoid having to type your name and password when returning to a forum... etc. This option deletes those cookies.
Bookmark icons: Many Web sites specify a icon (also called a "favicon"), which displays in the Address bar and alongside Bookmarks and addresses in the History menu. This option deletes those icons.
System Logs: This option deletes the various System logs stored in the folders /Library/Logs/, /Library/Logs/AppleFileService and /Library/Logs/DirectoryService/.
Applications Logs: This option deletes the applications logs in the folder ~/Library/Logs/.
Archived Logs: When the periodic scripts (daily, weekly and monthly) are run, log files are archived and compressed. There may be up to 7 archives per log. This option allows you to remove all of the compressed archives.
System CrashReporter: This option deletes System CrashReporter logs stored in the folder /Library/Logs/CrashReporter/.
Applications CrashReporter: When an application crashes, a log file is created in the folder /Library/Logs/CrashReporter/ in your Home folder. The daily script deletes log files not changed in the last 60 days. This option allows you to remove all files in the folder.
After clearing caches, restart the computer.
User Cache: This option allows you to remove certain files in the folder Library/Caches/ in your Home folder.
System Cache: This option allows you to remove System caches. Clean removes only a few files. Clear All removes the contents of the following folders: /Library/Caches/ and /System/Library/Caches/.
Recent Servers: Every time you connect to a computer, its address is stored in a file in the folder /Library/Recent Servers/. This option allows you to remove all such files.
Recent Items: This option allows you to remove the recent items in the File menu > Open Recent of these applications: QuickTime Player, TextEdit, Preview, iMovie, iPhoto, Xcode, PackageMaker, Icon Composer, Property List Editor, Interface Builder and Script Editor.
Reset Mac OS Help: This command deletes certain files that might cause problems when you want to show the Mac OS Help.
Links between documents and applications: Since Mac OS X 10.3.4, an alert message appears when you launch a new type of document for the first time. The link between this type of document and the application executed is stored in the "com.apple.LaunchServices.6B.csstore" file in the folder /Library/Caches/. This command deletes this file and reinits the links between your documents and the applications.
Be careful: the following command is irreversible.
Hidden Files .DS_Store: An invisible file .DS_Store maintains various information regarding the folder in which it is located (icon view and positions). On other systems, those files are not invisible. You can choose to remove them before burning a CD-ROM, for example... This option deletes all .DS_Store files from the hard disk
core.xxx Files: This option allows you to remove all core.xxx files located in the invisible folder /cores/.
Temporary Files: This option allows you to remove the temporary files in the folder /private/var/tmp/.
After the following VM operation, restart the computer.
Virtual Memory files: This option allows you to remove all swapfile files of the folder: /private/var/vm/.
Force empty Trash: Some files or folders in the trash will refuse to be deleted, notably when they are locked or if you don't have write permission for them. This option removes the contents of the Trash, regardless of privileges. The option 'Securely Delete', destroys the items before deleting them. After this command, the Finder is relaunched to update the Trash icon.
Jon
G4 1.33Ghz iBook, G4 iMac 1Ghz, G3 500Mhz iBook, Macintosh 128K, eMate... Mac OS X (10.4.3) Airport Express, Palm Zire 72, Minolta Dimage X31, iSight, and more
