7.3

SQL Server Database
IaaS uses a Microsoft SQL Server database to maintain information about the machines it manages, plus
its own elements and policies. Most users allow vRealize Automation to create the database during
installation. Alternatively, you may create the database separately if site policies require it.
Distributed Execution Manager
The IaaS DEM component runs the business logic of custom models, interacting with the IaaS SQL
Server database, and with external databases and systems. A common approach is to install DEMs on
the IaaS Windows server that hosts the active Manager Service, but it is not required.
Each DEM instance acts as a worker or orchestrator. The roles can be installed on the same or separate
servers.
DEM Worker—A DEM worker has one function, to run workflows. Multiple DEM workers increase
capacity and can be installed on the same or separate servers.
DEM Orchestrator—A DEM orchestrator performs the following oversight functions.
n
Monitors DEM workers. If a worker stops or loses its connection to Model Manager, the DEM
orchestrator moves the workflows to another DEM worker.
n
Schedules workflows by creating new workflow instances at the scheduled time.
n
Ensures that only one instance of a scheduled workflow is running at a given time.
n
Preprocesses workflows before they run. Preprocessing includes checking preconditions for
workflows and creating the workflow execution history.
The active DEM orchestrator needs a strong network connection to the Model Manager host. In large
deployments with multiple DEM orchestrators on separate servers, the secondary orchestrators serve as
backups by monitoring the active DEM orchestrator, and provide redundancy and failover if a problem
occurs with the active DEM orchestrator. For this kind of failover configuration, you might consider
installing the active DEM orchestrator with the active Manager Service host, and secondary DEM
orchestrators with the standby Manager Service hosts.
Agents
vRealize Automation IaaS uses agents to integrate with external systems and to manage information
among vRealize Automation components.
A common approach is to install vRealize Automation agents on the IaaS Windows server that hosts the
active Manager Service, but it is not required. Multiple agents increase capacity and can be installed on
the same or separate servers.
Virtualization Proxy Agents
vRealize Automation creates and manages virtual machines on virtualization hosts. Virtualization proxy
agents send commands to, and collect data from, vSphere ESX Server, XenServer, and Hyper-V hosts,
and the virtual machines provisioned on them.
Installing vRealize Automation
VMware, Inc. 13