Microsoft Windows XP Professional Resource Kit 2003
ISBN: N/A
EAN: N/A
EAN: N/A
Year: 2005
Pages: 338
Pages: 338
Offline Files provides access to network files and folders from a local disk when the network is unavailable. This feature is particularly useful when access to information is critical, when network connections are unstable, or when using mobile computers.
Offline Files gives mobile users access to their files when they are not connected to the network and ensures that they are always working with the most current version of the files. These benefits are also useful to onsite workers who might temporarily lose network connectivity due to server maintenance or technical problems. For more information about issues relating to offline files on mobile computers, such as synchronizing with a slow link and preventing synchronization when running on battery power, see Supporting Mobile Users in this book.
Offline Files can be paired with Folder Redirection for higher data reliability. For example, if a folder is redirected, the contents of that folder are stored on a server drive. In Windows XP Professional, by default any redirected folders are automatically made available offline. This default behavior can be changed by enabling the Group Policy setting, Do not automatically make redirected folders available offline. The folder is then accessible on the user s computer in case of network inaccessibility and from any computer to which the user logs on.
In an Active Directory environment, Group Policy settings control the Offline Files feature. For details about Group Policy settings that manage Offline Files, see Group Policy Settings that Affect Offline Files later in this chapter, and Group Policy Help.
An Active Directory environment is not necessary to use Offline Files. You can make files available from any computer that supports server message block (SMB) based File and Printer Sharing, including computers running Microsoft Windows 95, Microsoft Windows 98, Windows NT 4.0, and Windows 2000. Offline Files is not available on Novell NetWare networks or when Windows 2000 is running Terminal Services (except in single-user mode.)
Files specified for offline use are cached in a database on the hard disk of the local computer. If the network resource becomes unavailable, a message appears in the notification area. Changes made to the file while offline are saved locally, and then synchronized when the network resource becomes available again.
Before you can make files or folders on a computer available offline, you need to set up the computer to use Offline Files.
To set up a computer to use Offline Files
Open My Computer.
On the Tools menu, click Folder Options.
On the Offline Files tab, select the Enable Offline Files check box if it is not already selected.
Select Synchronize all offline files before logging off to enable a full synchronization. Leave this option unselected for a quick synchronization.
On the Offline Files tab, you can also set the reminder balloon options, designate the amount of disk space to use for offline files, place a shortcut to the Offline Files folder on the desktop, and encrypt the offline files local cache. Note that if an option is controlled by a Group Policy setting, it cannot be changed on the Offline Files tab of the local computer.
Offline files and related information are stored in a database in the system folder (systemroot\CSC) on the local computer.
| Note | Another term for Offline Files is client-side caching (CSC). |
The CSC directory contains all offline files that are requested by any user on the computer. The database mimics the network resource while it is offline so that files are accessed as though the network resource is still available. File permissions and system permissions on the files are preserved. For example, a Microsoft Word document created by Bob, given a password, and saved to a share on which only Bob has Full Control, cannot be opened from the CSC directory by Alice, because she has neither the share permissions to open the file nor the password required to open the file in Microsoft Word. You can also maintain the security of sensitive files by using Encrypting File System (EFS) to encrypt the Offline Files cache.
The Offline Files folder shows the files that are stored in the database. To open or view the files directly in the CSC folder, you must log on as a member of the Administrators group.
| Note | On a file allocation table (FAT) file system or a FAT file system converted to NTFS, users might be able to read information that is cached in the systemroot\CSC directory. This includes offline files that are requested by another user on the same computer. |
It is very important not to delete files directly from the CSC directory. For information about how to delete files see Deleting Files and Folders later in this chapter.
Files are cached either automatically or manually to the computer that requests them. Automatic caching occurs when a specific file in a folder is opened, but only if the server indicates that the contents of the share must be automatically cached. Automatically cached files are marked as Temporarily Available Offline in the Offline Files folder because they can be removed from the cache as the cache fills up. There is no guarantee that an automatically cached file will be available when offline.
Files are manually cached when a computer specifically requests, or pins, a particular file or folder on the network to be made available offline. You pin a file or folder by selecting the file or folder, and on the File menu selecting Make Available Offline. Manually cached files are marked as Always available offline in the Offline Files folder.
In Windows 2000 and Windows XP Professional, the Manual Caching for Documents setting is enabled by default when a folder is shared. To change the setting so that documents in the shared folder are automatically cached, right-click the folder, click Properties, click the Sharing tab, and then click Caching. In the Settings box, select Automatic Caching of Documents. You can also disable caching.
| Note | You can manually pin files and folders that are configured for automatic caching. |
By default, the following file types cannot be cached:
*.slm; *.mdb; *.ldb; *.mdw; *.mde; *.pst; *.db?
You can override the default settings by using the Files not cached Group Policy setting. Any file types that you specify in the Group Policy setting override the default settings. For example, if you specify that only .txt files cannot be cached, all other file types are available for caching.
The default cache size for automatically cached offline files is 10 percent of the total disk space of the hard disk. You can change the default by specifying a value between 0 and 100 percent on the Offline Files tab of the Folder Options dialog box. This setting does not affect the cache for files that are manually cached by the user, or for files pinned by the administrator using the Group Policy setting Computer Configuration\ or User Configuration\Administrative Templates\Network\Offline Files\ Administratively assigned offline files. You can store up to 2 gigabytes (GB) of automatically cached files per computer if that much space is available; for manually cached files, you are limited only by the amount of available disk space on the drive containing the cache.
| Note | If the network resource is online, renaming files in the Offline Files folder takes effect immediately on the network resource. |
Windows XP Professional provides Encrypting File System (EFS) support for Offline Files. The local cache of Offline Files can be encrypted if the cache directory resides on an NTFS volume. When the cache is encrypted, the local copy of a cached file is automatically encrypted.
| Tip | This capability is particularly useful for securing data on mobile computers. |
To select this option, in the Folder Options dialog box, click the Offline Files tab, and then select the Encrypt Offline files to secure data check box. You must be a member of the Administrators group to perform this function.
You can also use Group Policy to apply this option to groups of users. In the Group Policy snap-in, enable the Encrypt the Offline Files cache setting. If the setting is configured by using Group Policy, it cannot be overridden on the Offline Files tab on the local computer.
A network share automatically becomes available after being offline when three conditions are all met:
No offline files from that network share are open on the user s computer.
No offline files from that network share contain changes that must be synchronized.
The network connection is not a slow link.
If these conditions are met, a user can open a file and automatically begin working on that file on the network share. The changes the user makes are saved both to the file on the network share and to the file that is cached in the Offline Files folder.
If any of these conditions is not met and a user opens a file on the network share, the user continues working offline even though the network share is available. Any changes that the user makes are saved only to the local version of the file, which must then be synchronized with the network share.
When using Offline Files, users can synchronize some or all network resources by using Synchronization Manager. For example, users can set certain shares to be synchronized every time they log on or log off the network. Synchronization Manager quickly scans the system, and if it detects changes, the resources are automatically updated. Only the resources that have changed are updated, which speeds up the synchronization process.
Administrators can use Group Policy to specify that all offline files on a particular computer are automatically synchronized when users log off, when users log on, or when a computer enters a suspend state.
Offline files can be synchronized with the server copies of the files:
When the user manually forces synchronization.
During the logon or logoff process, as specified in Synchronization Manager.
At intervals when the computer is idle, as specified in Synchronization Manager.
At scheduled times, as specified in Synchronization Manager.
When synchronizing offline files, you can select quick synchronization or full synchronization. The full synchronization option synchronizes every file in the local cache with the network share. The quick synchronization option only verifies that all files in the cache are complete; it does not verify that they are up-to-date.
For example if you have an autocached share containing a 10-MB file named Example.doc, when the client opens Example.doc for the first time, a directory structure is created for the file in the client database, and the file is marked as incomplete. At this point, a directory entry with the file properties exists on the client, and Example.doc is a 0-byte length file. Example.doc is then read from the server in increments. If the application is closed before the entire file is read, the file is saved in an incomplete manner in the local cache. Incomplete files are not available offline. Quick synchronization completes such files.
By default, full synchronization is performed when the user logs off. If the Group Policy setting Synchronize all offline files before logging off is disabled, then the system automatically performs a quick synchronization.
In order for synchronization to work, the network resources must be online or available for reconnection. How synchronization is run affects how offline changes are sent to the network resource and how new versions of cached files are downloaded. Table 6-1 describes what kind of synchronization occurs when each method is used.
| Synchronization Settings and Functions | Send offline changes to the network resource? | Receive cached files from the network resource? |
|---|---|---|
| Automatically synchronize the selected items when I log on to my computer is enabled | Yes | No |
| Synchronize all offline files before logging off is enabled | Yes | Fully |
| Synchronize all offline files before logging off is disabled | No | Partially |
| Synchronize the selected items while my computer is idle | Yes | Partially |
| Scheduled by using Synchronization Manager | Yes | Fully |
| Clicking Synchronize from the Start menu or on the Tools menu | Yes | Fully |
| Clicking Synchronize on the File menu | Yes | Fully |
| Clicking Make Available Offline on the File menu | No | Partially |
| Clicking the Offline Files icon in the notification area of the task bar | Yes | No |
If the network resource version of a file and the locally cached version of the file are different, you can view each file and the date and time that the files were saved, and then select one of the following options in the Resolve file conflicts dialog box:
Keep both versions. Saves the version that resides on the local computer to the network as filename(username vX).doc, where filename is the name of the file, username is the user name, and X is the version number.
Keep only the version on my computer. Replaces the network version.
Keep only the network version. Replaces the version on my computer.
Use the following procedure to set up synchronization.
To set up synchronization
Open Synchronize.
Click Setup.
Use the Logon/Logoff, On Idle, and Scheduled tabs to configure options.
You can also initiate synchronization from the My Documents folder. After you have set up files for synchronization, Synchronize appears on the Start menu.
| Note | Synchronization works only for the user who is currently logged on. |
There are two methods you can use to safely remove offline files from the cache without affecting network files or folders. You can delete selected files from the Offline Files folder, or you can delete all files associated with a particular network share by using the Delete Files feature from the Offline Files property page. Do not directly delete or move any files from the systemroot\CSC folder.
You can open the Offline Files Folder and delete files directly from the list of offline files. Deleting a file this way removes it from the cache regardless of whether it was manually or automatically cached.
| Note | Deleting files and folders from the cache does not delete the network copy of the file or folder. |
If an offline folder is manually cached and you delete any or all offline files in the folder, the folder remains pinned. All files in the folder are cached the next time a full synchronization occurs.
To delete files from the cache using the Offline Files Folder
Click a folder, and then on the Tools menu, click Folder Options.
On the Offline Files tab, click View Files.
Click the files you want to delete, and then on the File menu, click Delete.
In this view of the Offline Files folder, you can see which files are automatically cached (temporarily available offline) and which are manually cached (always available offline). If you delete manually cached folders this way, the folders and files in them are no longer pinned. You need to pin the files or folders to make them available offline again.
To delete files from the cache on a network share
Click a shared network folder, and then on the Tools menu, click Folder Options.
On the Offline Files tab, click Delete Files.
In the Confirm File Delete dialog box, select the shared folders containing the offline files you want to delete.
Click Delete only the temporary offline versions if you want to delete files that were automatically cached. Click Delete both the temporary offline versions and the versions that are always available offline if you want to delete files that were automatically cached and files that were manually cached (pinned).
Files are also deleted from the cache whenever an offline file is deleted by using a normal user path, such as Windows Explorer, My Computer, the Run dialog box, or the command prompt. When users verify that they want to delete a file, the file is removed from the cache. This is not an effective way to clean up the cache because it also deletes files in the shared network folder. However, the files are deleted immediately only if the associated network share is online. If the share is offline, the local copy is deleted and the Synchronization Conflict notification is displayed during the next interactive synchronization.
During normal operation, you delete cached files by using the procedure shown in Deleting Files from the Offline Files Folder earlier in this chapter. However, if normal methods of deleting files are unsuccessful, you might need to reinitialize. Reinitializing deletes all offline files in the folder and resets the Offline Files database. If any files in the cache are changed and not synchronized with the network versions, the changes are lost when the cache is reinitialized. You must restart the computer to complete the reinitialization.
To reinitialize the Offline Files cache
Click a folder, and then on the Tools menu, click Folder Options.
Click the Offline Files tab.
Press CTRL+SHIFT, and then click Delete Files.
Restart the computer.
| Caution | You cannot undo the effects of reinitialization. After the cache is reinitialized all offline files are permanently removed from the computer. |
You can use Group Policy settings to control the functioning of Offline Files. In an Active Directory environment, you can apply these settings to groups of users by applying a GPO to a site, domain, or organizational unit. In a non-Active Directory environment, you can configure these settings in the local GPO, which is found on each client computer.
Note that many of the following settings can also be configured by the user by using the My Computer interface, as described in Implementing Offline Files earlier in this chapter. Generally, if you apply a GPO, but leave a setting as Not Configured, the user can configure it by using Offline Files in Folder Options. If you either enable or disable the setting, the user cannot change it.
For more information about using Group Policy with Windows 2000 Server, see Group Policy and Introduction to Desktop Management in the Distributed Systems Guide of the Microsoft Windows 2000 Server Resource Kit.
The Group Policy settings for Offline Files are found in two locations in the Group Policy snap-in: Computer Configuration\Administrative Templates\Network\ Offline Files for computer-based settings, and User Configuration\Administrative Templates\Network\Offline Files for user-based settings. Some settings are available for Computer Configuration only, while some are available for both User Configuration and Computer Configuration. If the same setting is configured for both Computer Configuration and User Configuration, the Computer Configuration setting takes precedence.
For more information about a setting, click the Explain tab associated with each Group Policy setting. Table 6-2 shows Group Policy settings for Offline Files.
| Group Policy Setting | Description |
|---|---|
| Enabled | Determines whether Offline Files is enabled. Offline Files is enabled by default on Windows XP Professional based client computers and is disabled by default on servers. |
| Default cache size | Limits percentage of a computer s disk space that can be used to store automatically cached offline files. Does not affect disk space available for manually cached offline files. |
| Files not cached | Allows you to exclude certain types of files from automatic and manual caching for offline use. |
| At logoff, delete local copy of user s offline files | Deletes local copies of the user s offline files when the user logs off. Caution: Files are not synchronized before they are deleted. Any changes to local files since the last synchronization are lost. |
| Encrypt the Offline Files cache | Determines whether offline files are encrypted in the cache on the local computer. Encrypting the offline cache enhances security on the local computer. |
| Disable user configuration of Offline Files | Prevents users from enabling, disabling, or changing the configuration of Offline Files. Administrators can configure other settings as they require, then enable this setting to prevent users from making any changes, thus locking in a standard configuration. |
| Synchronize all offline files before logging off | Determines whether offline files are fully synchronized when users log off. |
| Synchronize all offline files when logging on | Determines whether offline files are fully synchronized when users log on. |
| Synchronize all offline files before a suspend | Determines whether offline files are fully synchronized before a computer (such as a portable computer) enters suspend mode. |
| Action on server disconnect | Determines whether network files remain available if the computer is suddenly disconnected from the server hosting the files. |
| Non-default server disconnect actions | Determines how computers respond when they are disconnected from particular Offline Files servers. Administrators can enter the name of each server, and specify whether users can work offline when disconnected from that server. |
| Disable Make Available Offline tab | Prevents users from making network files and folders available offline. Removes the Make Available Offline option from the File menu and from all shortcut menus in Windows Explorer. Does not prevent the system from saving local copies of files that reside on network shares designated for automatic caching. |
| Prevent use of Offline Files folder | Disables the View Files button on the Offline Files tab. As a result, users cannot use the Offline Files folder to view or open copies of network files stored on their computer. Does not prevent users from working offline or from saving local copies of files available offline. Does not prevent them from using other programs, such as Windows Explorer, to view their offline files. |
| Administratively assigned offline files | Allows the administrator to specify files and folders available offline to users of the computer. To assign a file or folder, click Show and then click Add. In the Type the name of the item to be added box, type the fully qualified UNC path. |
| Do not automatically make redirected folders available offline | By default, local folders that are redirected are automatically made available offline. This setting allows the administrator to override the default behavior. |
| Prohibit Make Available Offline for these files and folders | Allows the administrator to specify files or folders that you do not want available offline. To assign a file or folder, click Show and then click Add. In the Type the name of the item to be added box, type the fully qualified UNC path. |
| Subfolders always available offline | Makes subfolders available offline whenever their parent folder is made available offline. |
| Disable reminder balloons | Reminder balloons appear above the Offline Files icon in the notification area to notify users when they have lost the connection to a networked file and are working on a local copy of the file. This setting hides or displays reminder balloons. |
| Reminder balloon frequency | Determines how often reminder balloon updates appear (in minutes). |
| Initial reminder balloon lifetime | Determines how long the first reminder balloon for a network status change is displayed (in seconds). |
| Reminder balloon lifetime | Determines how long updated reminder balloons are displayed. |
| Event logging level | Determines which events the Offline Files feature records in the Event Log. |
| Configure Slow link speed | Configures the threshold value at which the Offline Files component considers a network connection to be slow, to prevent excessive synchronization traffic. |