7.2

Manager Service
The Manager Service is a Windows service that coordinates communication between IaaS DEMs, the SQL
Server database, agents, and SMTP.
IaaS requires that only one Windows machine actively run the Manager Service. For backup or high
availability, you may deploy additional Windows machines where you manually start the Manager Service
if the active service stops.
I Simultaneously running an active Manager Service on multiple IaaS Windows servers makes
vRealize Automation unusable.
The Manager Service communicates with the Web server through the Model Manager and must be run
under a domain account with administrator privileges on all IaaS Windows servers.
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 workows. 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 workows to another DEM worker.
n
Schedules workows by creating new workow instances at the scheduled time.
n
Ensures that only one instance of a scheduled workow is running at a given time.
n
Preprocesses workows before they run. Preprocessing includes checking preconditions for workows
and creating the workow 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 conguration, 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.
Chapter 1 vRealize Automation Installation Overview
VMware, Inc. 13