ReliaSoft's Xfmea and RCM++ software products work with standard databases using the Microsoft Access file format in the back end for storing analysis data. This makes it possible to install and use the software without the need to purchase additional licenses for an enterprise database system (such as SQL Server or Oracle) and without requiring special IT infrastructure and support. However, Xfmea and RCM++ Standard database and library files (*.rx4, *.lb4, *.rx5, *.lb5) will be subject to the same limitations and vulnerabilities as any other Access database. For example, the limitations (in terms of maximum file size and simultaneous users) are publicized by Microsoft on the Web at http://office.microsoft.com/en-us/access/HP051868081033.aspx and some of the vulnerabilities are discussed in another Microsoft publication at http://support.microsoft.com/kb/283849/EN-US/. As this second publication states:

"Microsoft Jet, the database engine that is used in Microsoft Access, is a file sharing database system. When Microsoft Jet is used in a multi-user environment, multiple client processes are using file read, write, and locking operations on a shared database. Because multiple client processes are reading and writing to the same database and because Jet does not use a transaction log (as do the more advanced database systems, such as SQL Server), it is not possible to reliably prevent any and all database corruption." [emphasis added]

Although ReliaSoft's developers have made every effort to reduce or eliminate the possibility that the Xfmea/RCM++ software will induce a database error, there is no way to absolutely prevent corruption that might be caused by other factors, such as a faulty network hardware, an unexpected "crash" on your PC or a network interruption. Therefore, this document provides some recommendations for standard precautions that all users can take to protect the data in their Xfmea or RCM++ Standard databases from this type of corruption and reduce the impact of the data loss if corruption is unavoidable.

1. Create backups regularly
   • As with any file that contains a large amount of valuable information that would be difficult to re-create, it is essential to make sure that you are diligent about creating and storing backup files. There are a number of ways this can be accomplished:
     • If you select Automatically backup database upon closing from the Settings(2) page of the User Setup, Xfmea/RCM++ will automatically backup the database every time you close the file. This backup file will be stored in the same folder as the original files with the same name but with the extension *.rx4b.
       • For example, if the original database is at C:\Program Files\ReliaSoft\Xfmea4\Files\Database.rx4, then the backup will be at C:\Program Files\ReliaSoft\Xfmea4\Files\Database.rx4b.
     • If you select Database Tools from the Tools menu and then click the Create Backup button, the software will create a backup with a pathname/filename of your choosing. Each backup file will have the extension *.rx4b.
     • If you have a database open and select Export Database from the File menu, Xfmea/RCM++ will create a copy of the database to a pathname/filename of your choosing.
     • If you browse to the database file in one of the Windows file management tools (such as My Computer or Windows Explorer), you can copy and paste the database file.
2. Perform the "Compact and Repair" regularly
   • Using the "Compact and Repair" feature will help to reduce the size of the database file and help to protect against problems with the operation of the database. There are two ways that this can be accomplished in Xfmea/RCM++:
     • If you select Automatically compact and repair database upon closing from the Settings(2) page of the User Setup, Xfmea/RCM++ will automatically initiate this process every time you close the file (as long as the database is not currently in use by another user).
     • If you select Database Tools from the Tools menu and then click the Compact and Repair Database button, the software will initiate the process for the selected database file (as long as it is not currently in use by someone else).
3. Do not store the database in a shared network location if you suspect that your network connection and/or hardware may be unreliable
   • According to Microsoft, faulty network hardware is one of the main reasons why a file that uses the Microsoft Access database file format may become corrupted. As the Microsoft publication http://support.microsoft.com/kb/283849/EN-US/ states:

   "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." [emphasis added]  [Note that in Xfmea/RCM++ the extensions are *.rx4 or *.lb4 rather than *.mdb.]

   • If you have experienced this type of corruption for an Xfmea or RCM++ Standard database file, it is recommended that you take steps to correct the network problem or refrain from accessing database files over the network. In such cases, you may choose to upgrade to Xfmea Enterprise or RCM++ Enterprise (which use a SQL Server or Oracle database) or keep the analysis altogether in a single shared Standard database file but ask users to import the analysis to a separate "working" database on their own computers when there is a need to make substantial modifications. Users can then export the data back to the shared repository after the modifications are completed.
      
4. Do not allow the file size of the database to grow too large
   • Performance will be affected by the size of the database and the number of simultaneous users. Therefore, it is important for users to monitor the size of their database files and if they become too large, take steps to export the data into several smaller and more manageable files. Please be aware of the following factors, which can lead to very large database files:
     • Failure to "Compact and Repair" the database on a regular basis.
     • Using a very large number of "attached" documents. In some cases, using a "link" instead of an "attachment" may provide equivalent functionality with a much smaller impact on the size of the database file.

If you try to open an Xfmea/RCM++ Standard database via the software and receive a message that says "Unable to open the database" this is an indication that the database file may have become corrupted. Please contact ReliaSoft's Technical Support via phone, fax or e-mail and provide as much information as possible about exactly what you were doing when the corruption occurred. Whenever possible, please provide a copy of the corrupted file. In some cases, ReliaSoft may be able to provide assistance with salvaging some or all of the affected data. However, in many cases, the best recourse may be to restore the latest backup from before the corruption occurred.