Topic Last Modified: 2007-01-22

The Microsoft® Exchange Server Database Troubleshooter Tool detected one or more MSExchangeIS 9518 events with error code 0xfffffddc in the Application log. This indicates that the maximum number of transaction logs available for this storage group has been exceeded.


An MSExchangeIS 9518 event with error code 0xfffffddc is logged when it is trying to mount the databases of a storage group, and both of the following are true:

  • The maximum number of transaction logs available to this storage group has been exceeded.

  • All databases in the this storage group are in a Clean Shutdown state

Additionally, an MSExchangeIS 1159 event with error code 0xfffffdf9 should have been logged in the Application log before the affected databases shutting down. This event identifies that the Exchange Server has used all the available transaction log files for this storage group. When the last transaction log is filled, all databases within this storage group will be dismounted and cannot be restarted.

Exchange uses transaction log files that are numbered sequentially. In Exchange 2000 Server and Exchange Server 2003, transaction log files start with Exx00001.log, and then increment sequentially to ExxFFFF0.log. The maximum number of transaction log files that can be generated in a single sequence is 1,048,560 (0xFFFF0). Typically, it will take several years of operation before this many log files will be generated.

In Exchange Server 2007, the transaction log files are larger. There can be at most 2,147,483,647 log files (0x7FFFFFFF in hexadecimal, because log file names are in hexadecimal) in a log stream. The transaction log files are 1 megabyte (MB) each. This error will most likely not occur in Exchange Server 2007.

User Action

To resolve the error, you must remove all transaction log files and reset the transaction log file sequence back to 1. After resetting the log file sequence, the log file name is Exx00001.log in Exchange Server 2003 or older versions, and Exx00000001.log in Exchange Server 2007.

Use the Reset log generation number task in the Database Recovery Management tool that is part of the Microsoft Exchange Troubleshooting Assistant to perform this operation. The tool will verify that all databases were shut down correctly and then will safely move all transaction log files to a backup location.

The transaction log files can also be removed manually, but manual removal may result in a database in the storage group may not shutting down correctly and that database not being mountable again. To prevent such failures we recommend that you use the Database Recovery Management tool.

For more information and to download the tool, see Microsoft Exchange Troubleshooting Assistant v1.0.