Outlook OST File is in Use and Cannot be Accessed: Error Resolved

OST file gets created when Cached Exchange Mode is turned on and serves as the mirror image of Exchange DB mailboxes on the local machine. A replica of the Exchange mailbox data gets stored on client machine. The data can be deleted or modified even when there is no connectivity persists with EDB account.

The modified items get synchronized with EDB account when a connection is retrieved with Exchange Server. Sometimes, the OST file turns into inaccessible mode and shows "Outlook OST file is in use and cannot be accessed" error.

Reason for Existence of OST Error

There are different reasons responsible for the occurrence of this error message. This might takes place due to:

How to Rectify OST Error?

Several workaround and measures can be followed to eradicate the persisting Outlook OST file is in use and cannot be accessed error message. These include:

  • Execute ScanOST.exe
  • Convert OST to Outlook PST

Solution #1: Running ScanOST.exe:

The issues with the Offline Storage Tables can be eliminated by executing 'OST Integrity Check' tool. The inbuilt utility helps in rectifying minor corruption issues with these files. The only limitation with this utility is that it cannot repair files with higher corruption extents.

Note: ScanOST.exe is available in Outlook 2007 and lower versions and is not provided in latest versions of the application.

Step-by-Step Description for Executing ScanOST.exe:

  • Exit MS Outlook application.
  • Launch ScanOST.exe.

  • In case, if Outlook application is running, the following window will appear:

  • If the tool prompts for 'Profile name' provide the accurate name.
  • Further, if it prompts for 'Work Offline' or 'Connect', click on 'Connect'.
  • Select appropriate options such as 'Scan all folders' etc. as per requirement.

  • Select the 'Repair Errors' checkbox to command tool to automatically check and remove the discrepancies. Afterwards, Click on 'Begin Scan'.

Note: If the checkbox associated to the 'Repair Errors' is not tick-marked, the tool will check the issues but will not execute the appropriate corrections.

Detect OST Storage Location:

The location for the OST file can be detected by following the given procedure:

  • Click on 'Start' menu and type 'Run' in the available box.
  • In the 'Open' box, type


  • Next, locate the appropriate OST file in the then appeared Windows Explorer.

However, if there is major corruption exists in the file, it is suggested to convert OST file to PST for removing the existing error message. The procedure to implement this task is described in the upcoming segment.

Solution #2: Convert OST to Outlook PST

Due to absence of 'OST Integrity Check' tool in Outlook 2010 and recent versions, Microsoft recommends to convert OST to PST for removing the associated issues. This can be done via 'Import & Export' Option available in the application.

Procedure to Convert OST file to PST:

  • In 'File' tab, select 'Open' and then click on 'Import' option from right pane.

  • Select 'Import from another program or file' in the then appeared 'Import and Export Wizard'.

  • 'Import a file' window will appear, select 'Outlook data file (.pst)' and click 'Next'.

  • Click on 'Browse' and then select the file that has to be imported.

  • In the same window, select appropriate option to replace, allow or ignore import of duplicate items. Click on 'Next' button.

  • Provide accurate storage path for saving the converted file.
  • At last, click on 'Finish' to exit the wizard.

Note: The above stated procedure applies to Outlook 2013 and 2010 versions. The overall conversion process may vary in lower versions of the application.

Limitations Associated with Manual Recovery Methods

Though the procedure to run ScanOST.exe as well as to convert OST to PST is mentioned in this section, but these methods are associated with several limitations. They are quite lengthier and involve the possibilities of data loss. Manual conversion of offline files to Personal Storage Tables is not recommended as it might result in loss of crucial information stored in mailbox.

Moreover, the structure of email messages as well as the embedded attachments may lost their integrity while conversion. ScanOST.exe, the inbuilt utility, may help in removing minimal level corruption but is not helpful in eliminating higher level corruption issues. Moreover, the utility has been removed from the recent versions of the application. Therefore, the straight-forward and reliable third party tool can be utilized for getting rid of the OST error messages.

Get Access to Inaccessible OST

However, an easiest and simpler approach for rectifying "Outlook OST file is in use and cannot be accessed" error can be utilized to safeguard data from damage. RecoveryTools Exchange OST Recovery software can be employed for resolving OST related issues. The tool recovers offline file data and converts it to PST, EML, MSG and PDF format.

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