Help mobile users stay in sync

Windows 2000's Offline Files feature lets users who aren't connected to the network manipulate network-based files as if the users were connected. When the users log back on to the network, they can synchronize the changes they made locally so that the files on their local systems and on the network file share are identical. This capability is especially beneficial for mobile users and users who dial in from remote branch offices. To use Offline Files, you need to carry out two sets of configuration processes: one set on the server and one on the client computer.

Configuring the Server
To configure the server to use Offline Files, you must share the folder that holds the files you want to make available to offline users. Then, you must specify the way in which Win2K maintains those files on the server.

First, right-click the selected folder and choose Sharing from the context menu. This action takes you directly to the Sharing tab of the folder's Properties dialog box. Select the Share this folder option, as Figure 1 shows.

By default, Win2K gives the Everyone group Full Control permissions (i.e., permission to read, write, and modify) on shared folders. This setting usually is appropriate for file sharing because it permits all users to synchronize files they changed locally. To restrict access to files in the specified folder, you can substitute another group (or groups) for the Everyone group. Then, the users in the group that you specify are the only ones who can take advantage of Offline Files for this folder. If you want to change the permissions setting, click Permissions, then Add and Remove groups on the Permissions dialog box's Share Permissions tab.

Click Caching on the Sharing tab to open the Caching Settings dialog box, which Figure 2, page 90, shows. Select the Allow caching of files in this shared folder check box to make the files available for offline access. The options in the Setting drop-down list specify the way in which Offline Files will operate for the files in the specified folder. Choose one of the following caching settings: Manual Caching for Documents, Automatic Caching for Documents, or Automatic Caching for Programs.

Manual Caching for Documents. Manual Caching for Documents is the default setting and gives users offline access to any file in the folder. Users must select each file manually, and multiple users can access the same file for offline manipulation.

Automatic Caching for Documents. Automatic Caching for Documents automatically transfers any file a user opens to that user's local Offline Files folder. Users can't merely select a file for offline access; they must open the file.

Automatic Caching for Programs. Automatic Caching for Programs lets users access files for offline access but prevents synchronization of any changes that users make offline. In other words, a user can view a file, but when the user reconnects, Win2K doesn't upload any user changes. You can use this setting when a folder contains programs instead of (or in addition to) documents so that users can run the programs locally by transferring the executables to their local disks. However, be aware that many programs require additional files (e.g., DLLs) to run, so few programs can run in offline mode. Scripts and batch files are good candidates for this caching configuration option.

Some file types—primarily database data files—don't work properly (or at all) offline. By default, Win2K disables Offline Files for files with a .db?, .ldb, .mdb, .mde, .mdw, .pst, or .slm file extension. When you configure a folder that contains these file types to be available for Offline Files, Windows displays (for each ineligible file) the error message Unable to make file filename available offline on \\servername\sharename. Files of this type cannot be made available offline.

Configuring the Local Computer
To configure the local computer to use Offline Files, you must first confirm that the feature is enabled. (Offline Files is enabled by default on Win2K Professional systems but not on Win2K Server systems.) Open the Control Panel Folder Options applet or choose Tools, Folder Options from any Windows system window (e.g., My Computer, Windows Explorer, My Network Places) to open the Folder Options dialog box. Go to the Offline Files tab, which Figure 3 shows. Confirm that the Enable Offline Files check box is selected.

The other settings on the tab configure Offline Files' operation. The Synchronize all offline files before logging off option guarantees that users will get the most recent version of each offline-enabled file from the server when they log off. (Win2K automatically controls the synchronization process that occurs when users log on; you can't modify that process.)

The Enable reminders option controls the reminder balloon that appears over the taskbar system tray to help users remember that they're working offline. I suggest you select the Place shortcut to Offline Files folder on the desktop check box. Doing so provides a quick way for users to view their offline files. (Otherwise, users must navigate to the Folder Options' Offline Files tab and click View Files.)

The concept of temporary offline files can be confusing. By default, Win2K dedicates 10 percent of the local disk space to serve as a local cache when users open files in the folders that you've configured for automatic caching. Files are placed in this cache automatically when a user opens them. The files in this temporary cache aren't synchronized when users log on or log off, so you won't do any harm by reducing the size of the temporary offline files cache. You can use the slider at the bottom of the Offline Files tab to increase or decrease the amount of disk space that Win2K dedicates to the temporary cache. (This specification doesn't apply to the amount of disk space that the system dedicates to storing manually selected offline files. No specific limit exists for that space.)

Click Advanced to display the Offline Files - Advanced Settings dialog box, which Figure 4 shows. These settings let you specify the local computer's behavior when users lose a network connection. Notify me and begin working offline lets users continue working with any offline files that they've already moved to their local systems. Never allow my computer to go offline makes local offline files inaccessible until users can log on and log off properly to synchronize the files.

The Offline Files - Advanced Settings are global. However, you can customize the way client systems react when they lose a connection to a specific server. To do so, click Add in the Exception list section. In the resulting Offline Files - Add Custom Action dialog box, enter the name of the server for which you want to customize the connection-related settings, or use the Browse button to find and select the server's name. Then, choose the connection option you want to take effect if users lose their connections to that system.

The option you choose for handling an unplanned disconnection depends on the type of files users will access. If multiple users will access the same files, synchronization becomes more important to ensure that users are working with the most recent version of each file. If only one user will access the server-side file, that user can keep working offline when he or she is accidentally disconnected.

The Synchronization Process
File maintenance can get thorny when multiple users access the same file for offline use. Therefore, Win2K manages modified offline files during both the logon and logoff synchronization procedures.

Suppose User A and User B are both working offline with a file named file1. When User A then logs on, Win2K synchronizes the server-based file1 with the User A file1, so both files have the same content. When User B logs on, the system notes that User A's changes have been written to file1, so the server-based copy is different than it was when User B began working with it offline. Rather than overwrite User A's changes automatically, Win2K offers User B the choice of replacing the network file (i.e., the one with User A's changes), replacing the local file with the current version of the network file, or saving the modified local file, under a different filename, to the network. The appropriate choice is usually the option to save the file with a different name, giving both users access to each other's changes. During future synchronizations, users can decide which server-based file they want to make available for offline access.

When a file is accessible to many users, the number of files that are modifications of the original file can become enormous. Therefore, as an administrator, you might want to create multiple shares on your servers and limit the number of files in each share. (I'll discuss specific synchronization options and day-to-day use of Offline Files in my next Getting Started with Windows 2000 column.)

When a shared folder contains shared subfolders, and those subfolders contain files that users can access for offline use, the local computer's synchronization process ignores those subfolders. To permit subfolder synchronization, you must enable a local Group Policy.

Open a new Microsoft Management Console (MMC) console, then choose Console, Add/Remove Snap-in from the menu bar. Click Add to open the Add Standalone Snap-in dialog box. Select Group Policy, then click Add. By default, Local Computer is selected in the Group Policy Object dialog box. Click Finish, then click Close to return to the Add/Remove Snap-in dialog box. Click OK to return to the MMC console. In the left pane, expand the Local Computer Policy and navigate to Computer Configuration, Administrative Templates, Network, Offline Files. In the right pane, double-click the Subfolders always available offline policy, which Win2K doesn't configure by default. Click Enabled, then click OK to return to the MMC console. Close the console and choose No when you're prompted to save the console settings.

More to Come
After you configure the options for Offline Files on both the server share and the local computer, your users can begin to take advantage of the feature. In my next column, I'll cover the tasks that users must perform when using Offline Files and the way that Win2K implements those tasks. I'll also discuss some of the gotchas I've encountered with the feature. In the meantime, for more information about Offline Files, see Sean Daily, Tricks & Traps, "Daily Answers," May 2001, InstantDoc ID 20276; and Todd Logan, "The Ins and Outs of Offline Files," May 2001, InstantDoc ID 20373.