%1 (%2) %3Log sequence numbers for this instance have almost been completely consumed. The current log generation is %4 which is approaching the maximum log generation of %5, there are %6 log generations left to be used. To begin renumbering from generation 1, the instance must be shutdown cleanly and all log files must be deleted. Backups will be invalidated.

Details
Product: Exchange
Event ID: 514
Source: ESE
Version: 8.0
Symbolic Name: ALMOST_OUT_OF_LOG_SEQUENCE_ID
Message: %1 (%2) %3Log sequence numbers for this instance have almost been completely consumed. The current log generation is %4 which is approaching the maximum log generation of %5, there are %6 log generations left to be used. To begin renumbering from generation 1, the instance must be shutdown cleanly and all log files must be deleted. Backups will be invalidated.
   
Explanation

This Error event indicates that there are approximately 131,000 log file names remaining. The maximum number of transaction log files that can be generated in a single sequence is 2,147,486,647 (0x7FFFFFFF).  Typically, it will take dozens to hundreds of years of operation before this many log files will be generated.

You can calculate how long it will take you to exhaust the remaining logs by determining how many logs are generated on a typical day and then dividing 131,000 by that number for an approximate number of days remaining. This calculation will be a very rough estimate and is only valid the first time the event occurs.

However, you should immediately schedule a maintenance window where you can resolve the problem and prevent the storage group from disconnecting on its own when the available log file names are exhausted.

The transaction log file names have the following format: E0100012345.log, E01000ABCDE.log, E01000FFF00.log. The last eight characters of each log file name is the number of the log in the sequence. If ESE were to reach the last log generation number (0x7FFFFFFF), it would not be able to create another log file, and the database would be forced to shut down in a Dirty Shutdown state. To prevent this, all databases in the storage group will stop with the error Jet_errLogSequenceEnd when log generation 0x7FFFFFEC is reached (16 logs before the maximum). Stopping this far before the end of the sequence enables more than enough additional logs for the database to be returned to a Clean Shutdown state.

   
User Action

To recover from this problem, you must reset the log file sequence. To do this requires removing all existing transaction logs. After you do this, a new sequence of log files, starting with 0x00000001 will be generated.

Before removing transaction logs, you must verify that all databases in the storage group are in a Clean Shutdown state.

For more information about how to reset the log file sequence, follow the steps under WORKAROUND in Microsoft Knowledge Base article 830408, Store databases are dismounted without warning or users cannot log on to their mailboxes in Exchange Server 2003 or in Exchange 2000 Server.

If you are not already doing so, consider running the tools that Microsoft Exchange offers to help administrators analyze and troubleshoot their Exchange environment. These tools can help you make sure that your configuration is in line with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. Go to the Toolbox node of the Exchange Management Console to run these tools now. For more information about these tools, see Toolbox in the Exchange Server 2007 Help.

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