Integration Server 10.15 | Publish-Subscribe Developer’s Guide | Synchronizing Data Between Multiple Resources | Data Synchronization with webMethods | Echo Suppression for N-Way Synchronizations
 
Echo Suppression for N-Way Synchronizations
 
How the isLatchClosed Field Is Used for Echo Suppression
One other feature that Integration Server provides for data synchronization is echo suppression, which is also called latching. Echo suppression (or latching) is the process of preventing circular updating from occurring. Circular updating can occur when performing n-way synchronizations (data synchronizations where every resource can be a source and a target as well).
Circular updating occurs when the source subscribes to the canonical document that it publishes as illustrated in the diagram below.
Step
Description
1
A data change occurs on a source, and the source resource sends a notification document.
2
The source Integration Server builds and publishes a canonical document.
3
Because the source is also a target, it (as well as all other targets) subscribes to the canonical document via a trigger. As a result, the source receives the canonical document it just published. Logic on the source Integration Server uses the canonical document to build an update document to send to the source. The source receives the update document and makes the data change again. Because the source made this data change, it once again acts as a source to notify targets of the data change. The process starts again with step 1.
In addition to the source immediately receiving the canonical that it formed, it can also receive the canonical document many more times because other targets build and publish the canonical document after making the data change that the source initiated. See below for an illustration of this circular updating.
Step
Description
1
A data change occurs on a source, and the source sends a notification document.
2
The source Integration Server builds and publishes a canonical document.
3
A target receives the canonical document and makes the equivalent change.
4
Because the target made a data change, it sends a notification document for the data change.
5
The target Integration Server builds and publishes a canonical document.
6
The source receives the notification of the change that was made by the target and makes the change, again. This results in the process starting again with step 1.
To avoid the circular updating, Integration Server provides you with the following tools to perform echo suppression:
*The isLatchClosed field in the cross-reference table that you use to keep track of whether a resource has already made a data change or not.
*Built-in services that you use to manipulate the isLatchClosed field in the cross‑reference table to:
*Determine the value of the isLatchClosed field, and
*Set the value of the isLatchClosed column.