This alert indicates that a replication issue may affect the mailbox database copies in a particular Microsoft Exchange Server 2010 database availability group (DAG).

Exchange 2010 uses continuous replication to create and maintain database copies. To make changes to the mailbox store, the information store first records the database changes as database transactions in transaction log files. These files are written to the transaction log file storage location on the Active mailbox server. In response to requests from mailbox servers that host passive copies of the database, the transaction log files are copied to the transaction log storage locations on the passive mailbox servers. The Replay service on the passive mailbox server then replays these log files to the passive copy of the mailbox store.

If the volume that hosts the transaction logs for the passive database copy runs out of disk space, the passive database server can no longer receive transaction log files from the active mailbox server. Therefore, the passive database copy will not be synchronized with the active database, and the status of the passive copy changes to Failed.

A warning (yellow) alert is generated when the Windows Reliability and Performance Monitor LogicalDiskSpace\% Free Space object has a value that is 50 percent or less. When the object's value is 15 percent or less, a severe problem (red) alert is generated.

To resolve this error, do one or more of the following:

• Review the Application log and System log on your Exchange 2010 servers for related events. For example, events that occur immediately before and after this event may provide more information about the root cause of this error.
  
  
• Review the Operations Console in Operations Manager for detailed information about the cause of this alert. For more information, see the "Introduction" section in this topic.
  
  
• Check the following performance counter by using Microsoft Reliability and Performance Monitor:
  
  
  • Object: LogicalDiskSpace\% Free Space
    
    
• Examine the System log to determine whether any issues are affecting the disk subsystem.
  
  
• Move the transaction log storage location to a larger volume.
  
  
• Examine the memory and CPU usage on the passive mailbox server to determine whether paging operations or other operations are causing additional disk usage on the affected volume.
  
  
• Examine the current replication status for each replica database. To do this, use the Get-MailboxDatabaseCopyStatus cmdlet. To determine the replication status of a particular database copy, run the following command, as appropriate for the particular database:
  
  

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  Get-MailboxDatabaseCopyStatus -Identity <databaseName>

• You may have to suspend the database copy operations while you troubleshoot the disk usage issue. To do this, run the following command for each replica hosted on the affected volume:
  
  

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  Suspend-MailboxDatabaseCopy <databaseName>\<ReplicaServerName>

• If the database has been offline for an extended period, you may have to reseed it. To do this, follow these steps:
  
  
  1. Suspend replication to the database if it is not already suspended. To do this, run the following command:
     
     

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     Suspend-MailboxDatabaseCopy <databaseName>\<ReplicaServerName>

  2. Reseed the database copy. To do this, run the following command:
     
     

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     Update-MailboxDatabaseCopy <databaseName>\<ReplicaServerName> -SourceServer <ActiveServerName> -DeleteExistingFiles:$True

  3. Resume replication. To do this, run the following command:
     
     

     	Copy Code
     Resume-MailboxDatabaseCopy <databaseName\<ReplicaServerName>

For more information, see the following topics in Exchange 2010 Help:

• Understanding Mailbox Database Copies
  
  
• Understanding Database Availability Groups
  
  

If you are not already doing so, consider running the Exchange tools created to help you analyze and troubleshoot your Exchange environment. These tools can help make sure that your configuration aligns with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. To run these tools, go to the Toolbox node of the Exchange Management Console. To learn more about these tools, see Managing Tools in the Toolbox.