OL98: (CW) Compacting Outlook PST and OST Files

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NOTE: These procedures only apply if you have installed Outlook with theCorporate Workgroup/Other option. This option allows you to use MessagingApplication Programming Interface (MAPI) services. To determine yourinstallation type, on the Help Menu click About Microsoft Outlook. In AboutMicrosoft Outlook you should see "Corporate" if you have the CorporateWorkgroup installation.
This article describes how to compact the Personal Folders file (PST) orOffline Store file (OST) in Microsoft Outlook, to eliminate deleted itemspace and recover room on your hard disk.
More information
To conserve space on your computer's hard disk, you can delete unwanteditems from the various PST and/or OST folders and then compact the files tomake them smaller.

NOTE: Deleting the unwanted items from each folder only moves them to theDeleted Items folder, which is in the same file. You must delete the itemsfrom the Deleted Items folder to permanently delete them, so that Outlookcan compact the file.

The compacting process does not remove all the free space from the file.It leaves either 16 kilobytes (KB) or 4 percent of the file size (beforecompacting) whichever is greater.

To be compacted, a file must meet the following requirements:

  • The file must be 16 KB or larger.

  • The file must have at least 16 KB of space freed since the last time it was compacted.
You can start Outlook file compaction manually, or run it automatically inthe background.

Automatic Background Compaction

PST files that are not on your computer may require manual compaction, dueto interactions between the computer where the PST files are stored andyour computer.

Automatic compaction takes place as an idle task in the background. Thefollowing conditions must be true for this background task to take place:

  • Outlook must be running. -and-

  • The computer must not be engaged in other CPU-intensive tasks such as copying or downloading files.

To Manually Start PST Compaction

  1. On the Tools menu, click Services.
  2. Click to select Personal Folders, and then click Properties.
  3. On the General tab, click Compact Now.
  4. Click OK twice.

To Manually Start OST Compaction

  1. On the Tools menu, click Services.
  2. Click to select Microsoft Exchange Server, and click Properties.
  3. On the Advanced tab, click "Offline Folder File Settings."
  4. Click Compact Now.
  5. Click OK three times.
For additional information on compacting folders in the Internet Mail Only installation, click the article number below to view the article in the Microsoft Knowledge Base:
179870 OL98: (IMO) Compacting Outlook PST Files
98 outlook.pst mailbox.pst

Article ID: 179868 - Last Review: 11/01/2013 22:52:00 - Revision: 2.0

  • Microsoft Outlook 98 Standard Edition
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