Microsoft KB Archive/181406

= OL98: (CW) Purpose and Capacity of Outlook Storage Facilities =

Article ID: 181406

Article Last Modified on 12/2/2000

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APPLIES TO


 * Microsoft Outlook 98 Standard Edition

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This article was previously published under Q181406



NOTE: These procedures only apply if you have installed Outlook with the Corporate Workgroup/Other option. This option allows you to use Messaging Application Programming Interface (MAPI) services. To determine your installation type, on the Help Menu click About Microsoft Outlook. In About Microsoft Outlook you should see "Corporate" if you have the Corporate or Workgroup installation.



SUMMARY
This article discusses the purpose and capacity of each of the following storage facilities used by Microsoft Outlook 98 when running as a client to a Microsoft Exchange Server:


 * Personal Folders (.pst) files located on the user's computer.


 * Offline Store (.ost) files located on the user's computer.


 * Mailbox Folders located on the Microsoft Exchange Server.


 * Public Folders (PF) located on the Microsoft Exchange Server.



Personal Folders Files Located on Your Computer
One or more .pst files can reside on each user's computer. A .pst can be defined as your primary store or as a secondary store. A primary store means that mail delivered to the Inbox in that file and all of your other default Outlook folders, such as Calendar, Contacts, Deleted Items, Journal, Notes, Sent Items, and Tasks reside there. A .pst file can also be defined as a secondary store, which means you can move items to that file, either manually or with Inbox Rules, from your primary store.

Each .pst file can contain 16,384 items. An item is either a folder, message, task, etc. Each folder can contain a maximum of 16,384 items. If you select the option to "Allow upgrade to large tables," each folder can contain up to 65,536 items. The total file size of a .pst cannot exceed 2 Gigabytes (GB).

Offline Store Files Located on Your Computer
Only one .ost file can reside on each user's computer. The .ost is always defined as your primary store, meaning that your mail is delivered to the Inbox in that file and all of your other default Outlook folders, such as Calendar, Contacts, Deleted Items, Journal, Notes, Sent Items, and Tasks reside there. The .ost differs from the .pst in that items residing in it can also reside in the Mailbox on the server. You can synchronize the .ost and Mailbox folders so that they always contain the same information. This allows you to work offline when the server is unavailable; then when reconnected to the server, changes made offline will be uploaded to the server and then mail received while offline downloads to the .ost.

The .ost file can contain as many root folders as you desire and each folder can contain a maximum of 16 KB subfolders. If you select the option to "Allow upgrade to large tables," each folder can contain up to 64 KB subfolders. The total file size of an .ost cannot exceed 2 GB.

Mailbox Folders Located on the Microsoft Exchange Server
A Mailbox Folder for each user is stored on the server in the same database store. The server has a capacity of 16 GB for one store, however the server administrator may limit the size of each user's Mailbox Folder.

Note: this limitation does not apply to the Enterprise edition of Microsoft Exchange Server version 5.5. Store sizes are restricted to drive space installed and available on the server. If larger capacity drives are installed on the server, the stores can grow to the size available. This is not true of the Standard edition of Microsoft Exchange Server, which has the same store size limits as previous versions.

Public Folders Located on the Microsoft Exchange Server
Public Folders (PF) reside on the server in the same database store. They contain information shared by many users. Depending upon access permissions, individual users can read, update, or add to the Public Folder. The server has a capacity of 16 GB for one store.

