Design Manager Knowledge Base Article

Title/Subject:	Database corruption, networking problems, wireless networking issues, file integrity errors and errors 91, 3043, 3343, 3049
Category:	Any Product
Type:	Problem
Last Reviewed:	Saturday, June 10, 2006
Article ID:	10000043

Typical Causes of MDB File Corruption

There are three main causes of corruption in Design Manager/Jet .MDB files.

Database is Suspect/Corrupted Due to Interrupted Write Operation

You should always quit Design Manager properly by clicking Exit or Close on the File menu. If a database is open and writing data when Design Manager 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 Design Manager 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, a disk drive malfunction or the disk is full or nearly full (network or local hard drives), or NIC problem or malfunction. If any of these interruptions occur, then Jet may mark the database as potentially corrupted to prevent users from writing more data to the database and corrupting it further.

When Jet begins a write operation, it sets a flag, and resets the flag when the operation is completed. 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 corrupted. In most cases, the data in the database is not actually corrupted, 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.

Faulty Networking Hardware

In this case, the file corruption does not involve the Jet database 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, switches, routers, and hubs. The use of wireless networks, wireless routers, or direct VPN connections are not recommended because Jet clients manipulate the database directly making the database very susceptible to transmission errors and Internet conditions. Terminal Services or Citrix Metaframe should be used for remote connections or when a wireless network is the only option.

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.

Mixture of Computers on a Network in a Peer-to-Peer Environment

If you can, do not share a Microsoft Jet database file that is stored on a Microsoft Windows 95, a Microsoft Windows 98, or a Microsoft Windows Millennium Edition (Me) file share with Windows 2000/2003 clients. When you have a mixture of computers on a network, Microsoft recommends that you store and share the database file on a Windows 2000 Server with opportunistic locking disabled, Windows 2003 Server or on the newest operating system available when a server is not available. Corruption can occur if you have Windows 2000 or 2003 client computers share a file that is stored on a Windows 95, 98, Me, XP, Vista file share. This can occur even if the Windows 2000/2003 client have opportunistic locking disabled.

See:

http://support.microsoft.com/kb/q300216/