What is oab file in outlook

Outlook Offline Address Book OAB file is a collection of Outlook address book, which contains the name, email address and other contact details of Outlook users. We have also discussed the errors in Outlook Address file with their respective solutions.

Friday, January 14, About Contact. The two programs do not share a common codebase, but do share a common architectural philosophy.

The similar names lead many people to incorrectly conclusion that Outlook Express is a stripped-down version of Microsoft Office Outlook. Outlook Express utilizes the Windows Address Book to store contact information and incorporates tightly with it. Visit Developer Website. Microsoft Office Outlook. Microsoft Office Outlook Microsoft Outlook is available as a part of the Microsoft Office suite, and a personal information manager from Microsoft.

Although frequently used primarily as an email application, it also includes a calendar, task manager, contact manager, note taking, a journal and Web browsing. It can be utilized as a stand-alone application, or can work with Microsoft Exchange Server and Microsoft SharePoint Server for many users in an organization, such as shared mailboxes and calendars, exchange public folders, SharePoint lists and meeting schedules.

Developers can also make their own conventional software that works with Outlook and Office components using Microsoft Visual Studio. This will not change the file type. Only special conversion software can change a file from one file type to another.

Windows often associates a default program to each file extension, so that when you double-click the file, the program launches automatically. When that program is no longer on your PC, you can sometimes get an error when you try to open the associated file. Related Data Files. Are You Sure? Repair file extension issues on your PC. Start Download. All rights reserved. Terms Of Use Privacy Cookies. Summer Sale! Get My Deal Now. However, the Client Access services on any Mailbox server can proxy incoming OAB download requests to the correct location.

For instructions, see Use the Exchange Management Shell to configure any virtual directory in the organization to accept download requests for the OAB.

Autodiscover is supported by all versions of Outlook and virtually all mobile devices that are currently by Exchange. Here's a summary of the OAB distribution process:. The Client Access services on the Mailbox server that accepted the connection performs these steps:. Queries Active Directory again to find the mailbox database that hosts the organization mailbox for the OAB, and the Mailbox server that currently holds the active copy of the database.

If a shadow copy of the OAB exists in an organization mailbox in the local Active Directory site the site where the user is connecting from , then a local Mailbox server is used to download the OAB. However, synchronization of the shadow copy between organization mailboxes is performed on-demand. Here's how it works:. Let's say the organization mailbox doesn't have a suitable shadow copy of the OAB. This can be caused by the following conditions:. The shadow copy is out of date.

Shadow copies are aware when an updated copy of the parent OAB has been generated and published manually, or by the default 8 hour OAB generation schedule.

The affected Mailbox servers will stop distributing the outdated shadow copy to clients. This will trigger a full copy of the OAB from the parent to the shadow copy. The following events are reported:.

The job will be re-submitted. The job will not be resubmitted for the next hour. If the OAB is configured for shadow distribution, but there's no organization mailbox in the local Active Directory site the site where the user is connecting from , the Client Access services will proxy the OAB download request back to the Mailbox server that holds the organization mailbox for the parent OAB.

However, full OAB downloads are sometimes required. For example:. The Changes. Right-click the offline address list that you specified for your mailbox store, and then click Properties. In the result pane, click the Offline Address Book tab, and then select the offline address book that you want to configure. If you have increased the generation frequency of the offline address book files on your Exchange computer, you can also increase the frequency of the client offline address book downloads.

To do this:. Click your Exchange account, and then click to select the Include the selected account in this group check box. Under Select the options you want for the selected account group, make sure that the only check box that is selected is Download offline address book , and then click OK. Q Can I programmatically download an offline address book through the Outlook object model?

A No. Offline address book downloads are not exposed through the Outlook object model. Q I added a new user to Active Directory, but the user does not show up in Outlook. A The offline address book is not up to date.

Two events must occur before the changes show up in Outlook:. The server must generate the offline address book and include the changes in the differential files. If you are sure that the first event has occurred, you can perform a manual download of the offline address book. To do this, follow these steps:.

If you make frequent changes to the offline address book, you may want to modify the way that Outlook computers on your network access the Address Book. You can disable the downloading of the offline address book and force the Outlook computers to use the online Global Address List when they use Cached Exchange Mode. For more information about how to do this, click the following article number to view the article in the Microsoft Knowledge Base: How to prevent users from downloading the Offline Address Book without disabling Cached Exchange Mode As per this article, if offline address book.

To use this setting, you must set the registry value, remove any. Q What is the effect of offline address book downloads on the network? Will offline address book downloads flood the network? A When a cached mode profile is started for the first time, Outlook downloads the full offline address book from the server. This can affect the network, especially if multiple clients are starting up at the same time.

Other cases when Outlook clients require full offline address book downloads are described in question Differential downloads are not expected to cause a huge network impact if all the clients update the differential files on a daily basis. Outlook has the following safeguards that help protect the network from excessive offline address book downloads:. In the default configuration, Outlook will only try one full offline address book download in a hour period.

An attempt is counted when Outlook receives a response from the server and can at least start the offline address book download. In the default configuration, Outlook does not limit the number of attempts for differential updates. If a differential update fails, Outlook will retry the update after waiting one hour. Also, Outlook will not perform any full or incremental offline address book downloads if the client is running in header-only mode. To manually switch to header-only mode, point to Exchange Cached Mode on the File menu, and then click Download Headers.

Note The header-only mode configuration will only work with Exchange Q Under what conditions will Outlook perform a full offline address book download? A Outlook in cached mode will perform full offline address book download when the following conditions are true:. There is no offline address book on the client computer. This condition may occur if Outlook has not performed an initial complete synchronization. The total size of the differential files is greater than one-eighth the size of the full offline address book.

In this case, Outlook downloads the full offline address book for better performance. This condition may occur if there are lots of Active Directory objects that have a change to an attribute that is in the offline address book.

For example, phone numbers are updated with a new area code, departments are added to all users in Active Directory, and new address types are added. To modify the one-eighth rule, follow these steps. Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it.

Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:. This setting example 4 permits Outlook to download differential offline address book files that are up to one-fourth the size of the full offline address book. The parent distinguished name table changes.

When this behavior occurs, all Outlook clients will also try to perform a full download. A parent distinguished name is the part of a distinguished name also known as DN in an earlier Exchange format, not including the final relative distinguished name also known as RDN.

The parent distinguished name table is the set of all parent distinguished names that are found in Active Directory. They come from the legacyExchangeDN attribute and from the proxyAddresses attribute, and they start with the following prefix:. This means that x addresses for users who were migrated from another organization will not be included. There is a differential file missing on the server. Outlook cannot update to the current version without it. This behavior may occur if one of the following conditions is true:.

You did not start Outlook to log on to your Exchange mailbox for more than 30 days. The server policy permits only 30 days of differential files. The server was reset, or it crashed before it could post the differential files but after it was able to post the full offline address book files on the public folder. The version on the server and the version on the client do not match.

There is a more recent version of the offline address book present on the server. For example, Version 3a Unicode offline address book is now available, and you previously downloaded a Version 2 offline address book.

Applying changes to the offline address book failed. For example, differential files are corrupted on the server. Corruption may occur if the server goes down during differential file generation.