RES Automation Manager (AM) Master Dispatchers now enable an administrator to remove replicated SQL instances that have historically been used for scalability purposes. In prior versions of RES Wisdom, if two or more dispatchers are deployed over a WAN link it was recommended to place a replicated SQL instance on the remote site. The reasoning behind this was sound. As every Dispatcher talked directly to the SQL database placing two Dispatchers would require the resources to be downloaded twice. If we replicated the SQL database instance the resources would only traverse the WAN once as the Dispatchers would get their resources from the replicated SQL database instance.
Unfortunately the replication was only supported by Microsoft SQL Standard and up. Microsoft SQL Express was out the question so we had additional licensing costs. The setup and maintenance of SQL replication is also complicated and generally requires dedicated DBAs. Adding SQL database instances in large environments with many sites was challenging. Note: In large RES Wisdom/Automation Manager installations a replicated SQL instance is still highly recommended for resilience.
Enter 2010 and RES Automation Manager 2011! The new Dispatcher (now known as an “Engine”) model now includes the notion of Master and Slave Dispatchers. We don’t need to configure the Master Dispatchers per se, but we can point a “Slave” Dispatcher at a particular “Master” Dispatcher (or Master Dispatcher List). Now if there is more than 1 Dispatcher required at a remote site, we configure all but one as Slaves and the resources are only downloaded once over the WAN via the Master Dispatcher. The “Slave” Dispatchers download their resources from their Master Dispatchers; no more additional Microsoft SQL licensing and no need for DBAs (if you don’t already employ them!).
From a “RES Wisdom/Automation Manager Service Provider” (RAMSP – yes I did just make that acronym up!) point of view it now means you can protect your SQL instance and configure all remote Dispatchers as Slave Dispatchers, pointed at the hosted Master Dispatchers. Only the hosted Master Dispatchers will ever need to talk the SQL database improving security and reducing the number of open ports.
Note: It is possible and supported to daisy-chain or tier the Engines. I have no confirmation on the official tested/support limits, but being able to tier the AM Engines to two or three levels deep should enable us to support even the largest infrastructures (just wish Workspace Manager used this model 
). Kudos RES!
