Anyone who has lost a document because of a power outage knows the frustration of lost or corrupt data (PDF). Frustration could turn to panic if you discovered your entire database was corrupt. The possibility of data corruption is present regardless of the environment or database.

Data corruption does not occur by itself. Almost always at fault are the forces that move, control, and store the data. When information is transmitted electronically, data can become corrupt. In a simple network, information must pass from hard disk to bus to memory to network card to cable and back again, billions of times a day. If any link in this chain is faulty, information can be lost or corrupted. Here are some things to consider:

  • Power:
    An IBM study showed a typical computer is subject to more than 120 power problems a month. These problems often go unnoticed but can result in partial data loss or hard disk crashes. Many hardware devices can monitor and supplement your power supply. At a minimum, consider buying an Uninterruptible Power Supply (UPS) for your file server. UPS devices regulate power spikes and sags and ensure that your workstations receive an even amount of power. Most
    UPS devices have batteries that protect your data in the event of a power outage.
     
  • Hard Disk/Disk Controller Problems: Although your hard drive is hard, it is not impervious to wear and tear. Application data written to a damaged sector on a hard drive or written incorrectly will almost certainly be unreadable and useless. Following are symptoms of a faulty hard drive:
    • Disk I/O error during read
    • Error 57l
    • Continual data corruption (every day)
    • An increase in Hotfix "Redirected bytes area" (NetWare)
    • Disk controller errors in the NT Server EventLog
    • Sector not found reading drive c:\

    If you think you have a faulty or damaged hard drive, run a disk utility program such as Vrepair for NetWare or Norton Utilities for NT to help you isolate the problem.

  • Network Cards/Cabling:
    If your file server is sound and it appears only network data is corrupting, your cabling or network card may be faulty. To further isolate the source of corruption, perform this test on each workstation: copy a large file (40-50MB) from a workstation to the file server (e.g., C:\file.txt to F:\file.txt). At a DOS prompt, type FC C:\file.txt F:\file.txt /B. If the file compare responds with "no differences encountered," the source of corruption is probably elsewhere. If the file comparison returns differences in the files, consider replacing the cable link or network card.
     
  • Abnormal Application Termination:
    Turning your workstation off with the software still open can corrupt your data. Imagine your workstation is telling a story on the phone (via network cable) to the file server. During the story, the phone line goes down or your workstation hangs up. The connection is broken, and the file server is now left to determine the story's meaning after hearing only the first two chapters. Application errors or freezing can make resetting your workstation unavoidable, but we recommend you always try to exit your applications and Windows correctly.
     
  • Peer-to-Peer Networking:
    We do not recommend you use any of our software on peer-to-peer networks. In traditional network environments, all critical data is stored on a dedicated file server, whose sole function is to provide data to all connected workstations. In a peer-to-peer network environment, there is no dedicated file server. Instead, data is stored on a workstation acting as a file server. Because this workstation plays a dual role, application performance and stability can be compromised. When you restart the server/workstation, all connected workstations are disconnected. If the software application is open on a connected workstation when you restart the server/workstation, the chances for data corruption are increased.
     
  • Operating System:
    Network and desktop operating system features can adversely affect database applications. We recommend you not use these features:
    • Netware Client32 - Opportunistic Locking
    • Netware Client32 - Packet Burst
    • Windows NT Server - Opportunistic Locking
    • CPU or System Board Caching.
       
  • Steps to Minimize Data Loss:
    To minimize the chances of data loss or corruption, we recommend the following: