• If Exchange writer is in failed state, normally just rebooting the Exchange server will bring back the writer status to 'stable' state. Check the writer status by running the command 'vssadmin list writers' from command prompt on Exchange Server.
• Review other backup provider schedules including the Microsoft Exchange Database Maintenance Schedule to ensure that backups time frames are not conflicting. Adjust accordingly to resolve the error.

1. Click Start, point to All Programs, point to Exchange Server 2007, and then click Exchange Management Console.
2. Expand Server Configuration, and then expand the storage group that is listed in the event ID 9840 message that was logged on the Exchange 2007 server.
3. Right-click each database in that storage group, and then click Dismount Database.
4. Click Yes to confirm the operation.
5. After the dismount operation is complete, right-click the database again, and then click Mount Database.
6. Try to perform the backup operation that resulted in event ID 9840.
    

1. Click Start, point to All Programs, point to Administrative Tools, and then click Services.
2. Right-click Microsoft Exchange Information Store, and then click Restart.
3. Try to perform the backup operation that resulted in event ID 9840.

 If issue still persists, Please contact Microsoft Support for further assistance.

In order to verify that no snapshots are present, follow these steps:

1. Open a command prompt on the Exchange server and type the command "Vssadmin list Shadows".
2. If a snapshot exists, it will be listed. Before attempting to delete the snapshot make a note of the time at which it was taken. This will help to determine if the orphaned snapshot was created during or outside a backup. If the snapshot was created outside a backup, check for scripts or application that could have created it (for example some applications take snapshots by creating Scheduled Windows tasks).
3. Make a note of the ShadowId and use command "Vssadmin delete shadows /Shadow=<ShadowId>" to delete it.

It is also suggested to run Windows updates and install all available hotfixes on Exchange Servers and reboot.

The writer timeouts if there is another snapshot process is completing or in process:

If run command "vssadmin list writers" it will show Exchange writer status in Failed State 9. Here, need to check if no other third party application using VSS, like Volume level Shadow Copies on the system drives. If so, need to disable the Shadow Copies on these drives. Kindly note that disabling the shadow copies for the drive will delete all existing Shadow Copies.

This error "V-79-57344-65233 - A failure occurred querying the Writer status.", can also occur during Exchange Incremental backup of a SBS 2011:

It will give similar errors in the job log:

Writer Name: Exchange Server, Writer ID: {76FE1AC4-15F7-4BCD-987E-8E1ACB462FB7}, Last error: The VSS Writer failed, the process can be repeated (0x800423f3), State: error during the backup preparation (7).

Writer Name: Exchange Server, Writer ID: {76FE1AC4-15F7-4BCD-987E-8E1ACB462FB7}, Last error: The VSS Writer failed, the process can be repeated (0x800423f3), State: error during the blocking process (9).

This error causes if Circular Logging is enabled on Exchange. A differential or Incremental backup cannot be done if circular logging is enabled. To perform Incremental or differential type of backups, the logging method on Exchange needs to be changed by disabling the Circular Logging. Refer www.symantec.com/docs/TECH11310