Displays the date, time and domain controller that last backed up each writable directory partition in the forest by reading ...

Displays the date, time and domain controller that last backed up each 
     writable directory partition in the forest by reading the DSASignature 
     attribute on the root of the NC head of each directory partition

     The DSASignature attribute is populated on Windows 2003 Service Pack 1
     and newer domain controllers after a legacy or VSS (Volume snapshot 
     service) system state backup is performed. 

     Backup dates are not reported for Read-only partitions. 

     Domain controller prior to Windows Server 2003 Service Pack 1 do not 
     update the DSASignature timestamp.

     Failure to perform a timely backup is identified by NTDS Replication event 
     2089. 

     The Backup event threshold for event 2089 is controlled by the registry
     key "HKLM\SYSTEM\CCS\Services
TDS\Parameters\Backup Latency Threshold 
     (days)" (reg_dword) 

     The default is conservatively set to half of TSL but should be configured
     to 1 day in production environments.

     Backup frequency is examined 1x per day during the replication latency 
     check that generates events 1862, 1863, 1864. 


     For more information see MSKB article:

     http://support.microsoft.com/default.aspx?scid=kb;EN-US;914034 

     [SYNTAX]

     /showbackup 

     [EXAMPLES]

     repadmin /showbackup site:HQ