Article ID: 109953 - View products that this article applies to.
This article was previously published under Q109953
Novice: Requires knowledge of the user interface on single-user computers.
Environmental factors may leave your database file damaged. The symptoms of a corrupted database can range from #Deleted appearing in certain records, to the inability to open one of the objects in the database, to the complete inability to open the file in Access. The Repair and Compact utilities in Microsoft Access are useful tools for recovering and optimizing Microsoft Access database files. This article describes these utilities and offers additional alternatives for repairing damaged databases. Also, information on what can cause corruption is provided.
NOTE: This article only covers databases prior to Access 97. For additional information about troubleshooting databases in later versions of Access, click the article numbers below to view the articles in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/279334/EN-US/ )ACC97: How to Repair a Damaged Jet 3.5 Database
(http://support.microsoft.com/kb/209137/EN-US/ )ACC2000: How to Repair a Damaged Database
Although the steps outlined in this article are usually successful in recovering damaged database files, to safeguard your data, you should create a backup copy of your database file as often as you can.
The Repair and Compact Utilities
The Repair UtilityThe Repair utility can fix databases with certain types of damage. It tries to repair only the tables, queries, and indexes in the database. It does not try to repair damaged forms, reports, macros, or modules; it does, however, copy them to the new, repaired database.
NOTE: Run the Repair Database command only when the Microsoft Jet database engine returns an error message indicating that the Repair should be run. The Repair Database command should not be run under any other circumstances.
Compact UtilityThe Compact utility eliminates empty space in an existing database. It does so by creating a new destination database and copying each object in the old database to the new one. If you choose to compact the database into the original database name instead of a new database, the Compact utility creates a temporary database, exports all the objects from the original database into the temporary database, removes the original database, and renames the temporary database to the original database's name.
IMPORTANT: Compacting the database often is the best preventive maintenance for a .mdb file. The following is a list of actions the Compact utility performs.
Important Guidelines for Compacting a DatabaseBefore compacting a database, the following conditions must be met:
The user compacting the database must be logged on using an account that has Modify Design or Administer security permissions for all tables in the database. For more information on Microsoft Jet security, see Chapter 10, "Managing Security."
Sufficient disk space must exist for both the original and compacted versions of the database, even if the database is being compacted through the Microsoft Access user interface using the same file name. The compacted database is renamed as the original database only when compacting is successful.
Other users must not have the database open. When a database is compacted, it has to be open exclusively by Microsoft Jet to prevent any users from accessing and modifying the database during the process.
Recovering a Damaged DatabaseNOTE: If you are experiencing Microsoft Jet 3.x error numbers 3197, 3343, or 3015, please also refer to the following article in the Microsoft Knowledge Base:
182867The following steps outline a general method for repairing a damaged database:
(http://support.microsoft.com/kb/182867/EN-US/ )ACC: Jet Database Engine 3.x Error Messages Due to Corruption
172733If you cannot repair the database with these steps, the database is probably damaged beyond repair. If this is the case, you should restore your last backup database or re-create the database.
(http://support.microsoft.com/kb/172733/EN-US/ )Updated Version of Microsoft Jet 3.5 Available for Download
As a final alternative, some consultants may provide a Microsoft Access database repair service. Because this is such a specialized service, the most efficient way to locate a consultant is to post a message in the Microsoft Access "Third Party and User Groups" Internet newsgroup, which has the following newsgroup address:
microsoft.public.access.3rdpartyusrgrpFor more information about the Microsoft Access Internet newsgroups, please see the following article here in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/150057/EN-US/ )ACC: Microsoft Access Newsgroups Available on the Internet
Typical causes of mdb file CorruptionThere are three main causes of corruption in Access/Jet mdb files:
Database is Suspect/Corrupted Due to Interrupted Write OperationProper shut down, by clicking Exit or Close on the File menu, is highly recommended. However, if a database is open and writing data when Access is abnormally shut down, the Jet database engine may mark the file as suspect/corrupted. This can happen if the computer is manually turned off without first shutting down Windows or if power is lost. Other situations may not shut down Access but may still interfere with Jet's writing of data to the disk while the database is open. This can happen, for instance when Networks experience data collisions or disk drives malfunction. If any of these interruptions occur, then Jet may mark the database as potentially corrupted.
When Jet begins a write operation, it sets a flag, and resets the flag when the operation is complete. If a write operation is interrupted, the flag remains set. When you try to open that database again, Jet determines that the flag is set and reports that the database is corrupt. In most cases, the data in the database is not actually corrupt, but the set flag alerts Jet that corruption may have occurred. In cases such as this, compacting and/or repairing the database can typically restore the database. Fortunately, there are ways to determine which user and workstation was responsible for marking the file as suspect. See Methods to determine which users and/or workstations are causing Jet to mark the file as suspect later in this article.
Faulty Networking HardwareIn this case, the file corruption does not involve the Jet Engine; rather the file is literally corrupted by some outside cause. The cause can be one or more links in the hardware chain between the computer that the database resides on, and the computer that has the database open. This list includes, but is not limited to, network interface cards, network cabling, routers, and hubs.
Hardware based corruption is typically indicated by mdb files that cannot be restored through the use of compacting, repairing, or Jetcomp. Hardware corruption will typically recur until the responsible hardware is repaired or replaced.
Opening and Saving the .mdb File in Another ProgramThere is no way to recover a .mdb file that was opened and then saved in a different program. For instance, Microsoft Word will allow you to open an Access database and then save it (By the way, it does not serve any purpose if you open a .mdb file in another application since all you see are extended characters). Saving it this way will cause the mdb file to prompt you for a database password when trying to open it in Access--even though the file may have never been password-protected in Access. The password prompt occurs in such cases because the first byte range Access checks when opening a file is where the database password would be. If that byte contains corrupt data, Access treats the file as being password protected. Even if there were a way to get around the password prompt in this case, the database would still be unrecoverable because the binary structure is scrambled and thus unreadable to Access. Recovering a backup copy of the file is the only solution in this case. For additional information on this issue, click the article number below to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/223043/EN-US/ )ACC: Database Password Appears Even Though It Was Never Set
Steps that can be taken to prevent corruption
For more information about repairing databases, click Contents and Index on the Help menu, click the Index tab in Access Help, type the following text:
and then double-click the selected text to go to the Repair a damaged database topic.
Article ID: 109953 - Last Review: January 26, 2005 - Revision: 2.1