The only mandatory requirement SnowMirror has is a user account with sufficient rights to download the data. It is highly recommended, though, to activate one ServiceNow plug-in. Let’s have a look why it is a good idea to have the plug-in enabled and what it affects. It is perfectly OK to run SnowMirror without any ServiceNow modifications or plug-in activation. However, SnowMirror is always showing you some orange notification that a plug-in should be enabled. The documentation talks about the same and even SnowMirror support says it should be done. Why? And which plug-in is needed? The plug-in is called Aggregate Web Service Plug-In and it adds several web service operations enabling to execute aggregate queries. Such as count records, sum values, etc.
SnowMirror is showing progress during the synchronization run. Nevertheless, if the plug-in is not enabled there is no information about how many rows will be inserted, updated and deleted before the data is really downloaded. So the progress bar is a bit fake widget. It usually stops on 28% for a long time even if it is still downloading a lot of data. Yes, we admit, we tried to make it nice even if there is no information for the bar.
The second feature that does not work is a row counter. Every time a new synchronization is being created there is an extremely useful button Count Records. Why useful? It tells you how many rows the table has. Or how many rows it is going to be if an encoded query is used. Imagine you have a task table with 10M+ records. However, you only need a small subset of the table so you use encoded query feature. How do you know how many records it will be? Is the query working? Without the aggregate plug-in this great feature is not available. A warning note is displayed instead.
To activate the plug-in you need admin rights. Go to System Definition -> Plugins and activate the second plug-in available called Aggregate Web Service. After the activation please restart SnowMirror or clear caches in the SnowMirror Settings menu option.
If the plugin is active the Count Records feature is available and you can check even during a sync setup how many rows will be replicated.
The progress bars become more useful as well. As the aggregate ServiceNow functions return the number of new and altered records the progress bar shows a reality and not just fake numbers.
As a conclusion we always recommend to activate the Aggregate Web Service plug-in for production environments even if it works correctly without it. Not only it improves usability of SnowMirror but it helps the synchronizing algorithm to optimize the job too. The only situation where SnowMirror could be used without the plug-in is an evaluation period. You don’t have admin access to the instance or you do not want to alter the instance just to test SnowMirror if it fits your needs.
