Backlog Column Set

After addressing issues shown in the Error Conditions column set, the next column set to investigate is Backlog. This column set shows the backlog most common situations that require attention. The additional information in this column set is:


Shows the number of outbound connections for this member in this replica set. This is helpful for identifying which computers are hubs in the replication topology.


This indicates that a number of connections from this member is in a state where the maximum number of files are being replicated in parallel. If this persists, troubleshoot as described below and in the next chapter.

BacklogFiles and BacklogSize

Look for servers with unusually high numbers of files backlogged awaiting replication, or large total quantities of data to replicate. If this persists, troubleshoot as described below and see the section Backlogged Files.

  1. Backlogs are actually a per-connection property. Because Sonar just shows per-member information, it only displays the most backlogged connection for this member.
  2. Number of files backlogged is determined by examining the difference between the change order sequence numbers: BacklogFiles = NextChangeOrderSeq – TrailingChangeOrderSeq. However, there are some cases where this metric gets distorted: A vvjoin operation creates directed change orders, which only go to one partner, but Sonar does not take account of this possibility in this metric.


See Error Conditions Column Set for details.


This actually shows how many files are waiting to be installed on this computer (this list is known as the inlog or inbound logs). Files are most commonly in this state if there is a sharing violation preventing a file being installed; however, there are other potential reasons why a change order might wait in the inlog. See Sharing Violations for more information.


This shows computers that are in the process of joining (performing an initial synchronization) with their replication partners. Note that this process can occur in normal operation, and might cause a temporary replication backlog.


This shows the total number of VVjoins (or attempted VVjoins) this computer has been involved in since it restarted. This is not an indication of an error, because VVjoins can occur in normal operation.